🍌 Banana Walnut Layer Cake — Soft Sponge with Custard, Bananas & Crunchy Walnuts

Soft, tender sponge layers cradle silky custard, ripe banana slices and a satisfying walnut crunch — this Banana Walnut Layer Cake is a celebration of texture and balanced sweetness. It’s elegant enough for special occasions yet homey and approachable for afternoon tea. Follow this complete guide for foolproof sponge, creamy custard filling, assembly, decoration ideas, troubleshooting, and storage. 🌰🍰

Why this cake works

The recipe balances an airy, neutral-flavored sponge (oil + milk gives moistness and tenderness) with a cooked custard that adds stability and richness. Fresh banana slices add immediate fruity flavor; walnuts contribute crunch and a toasty note that contrasts the creamy filling. Moistening the cake layers with a little milk prevents dryness without making them soggy.

Ingredients (organized & with weights)

For the sponge cake (makes two 8–9″ layers or three thinner layers)

• 4 large eggs (about 200 g without shells)
• 1 cup (200 g) granulated sugar
• ½ cup (120 ml) milk — whole milk recommended
• ½ cup (120 ml) vegetable oil (neutral-flavored)
• 1½ cups (190 g) all-purpose flour, sifted
• 1 packet (10 g / 2 tsp) baking powder
• 1 tsp (5 ml) pure vanilla extract
• Pinch fine salt (¼ tsp / 1.5 g)

For the custard cream (stirred pastry cream)

• 3 cups (720 ml) whole milk
• 3 tbsp (24 g) all-purpose flour
• 2 tbsp (16 g) cornstarch
• ½ cup (100 g) granulated sugar
• 1 large egg yolk (about 18 g)
• 1 tsp (5 ml) vanilla extract
• 1 tbsp (14 g) unsalted butter
• Optional: 100 ml heavy whipping cream (chilled) — to fold in for lighter texture

For the filling & topping

• 2–3 ripe bananas (sliced; 300–400 g total peeled weight)
• ½ cup (60 g) walnuts, finely chopped and lightly toasted
• Milk for moistening layers — 2–4 tbsp (30–60 ml)
• Whipped cream or remaining custard for the top and sides
• Optional decorations: banana slices, walnut halves, toasted coconut flakes, chocolate shavings

Equipment & pan sizes

• Two 8–9 inch (20–23 cm) round cake pans (or one 9″ pan and slice into 2 layers)
• Parchment paper rounds and nonstick spray
• Mixing bowls, whisk, spatula
• Medium saucepan for custard, fine mesh sieve
• Electric mixer for whipping cream (if using)
• Cake turntable and offset spatula (optional but helpful)

Step-by-step instructions

1. Make the sponge — method & tips

1. Preheat the oven to 170°C / 340°F. Grease two 8–9″ pans and line the bottoms with parchment rounds.
2. In a large bowl, whisk together 4 eggs and 1 cup sugar until pale and slightly thickened — about 2–3 minutes by hand or 1–2 minutes with an electric mixer. This step provides lift and a light crumb.
3. Add ½ cup milk, ½ cup vegetable oil, and 1 tsp vanilla; whisk to combine. The oil keeps the sponge moist and tender.
4. In a separate bowl, sift together 1½ cups flour, 1 packet (10 g) baking powder, and ¼ tsp salt.
5. Fold the dry ingredients into the wet mixture gently in 2 additions until just combined — do not overmix. Stop when no streaks of flour remain.
6. Divide the batter evenly between the prepared pans. Smooth tops gently.
7. Bake at 170°C / 340°F for 30–35 minutes or until a toothpick comes out with a few moist crumbs and the top springs back gently.
8. Cool 10 minutes in the pans, then invert onto a rack to cool completely. If making three layers, slice horizontally once cool using a serrated knife or cake leveler.

2. Make the custard (stirred pastry cream)

1. In a medium saucepan, combine 3 cups (720 ml) milk and half the sugar (½ cup × ½ = ¼ cup if you prefer less sweet) and warm until steaming (do not boil).
2. In a bowl, whisk together 3 tbsp flour, 2 tbsp cornstarch, remaining sugar, and 1 egg yolk until smooth.
3. Temper the yolk mixture by whisking in a ladle of warm milk, then pour the tempered mixture back into the saucepan while stirring continuously.
4. Cook over medium heat, stirring constantly and scraping the bottom, until the mixture thickens into a custard-like consistency — about 3–6 minutes.
5. Remove from heat, stir in 1 tbsp butter and 1 tsp vanilla. For extra silkiness, pass the custard through a fine-mesh sieve into a clean bowl.
6. Cover the surface with plastic wrap to prevent a skin from forming and chill until cool. If using, whip 100 ml heavy cream to soft peaks and fold gently into cooled custard to lighten (this gives an English-style lightness and spreads more easily).

3. Toast the walnuts

1. Spread walnuts in a single layer on a baking sheet and toast in a 170°C / 340°F oven 6–8 minutes until fragrant, or toast in a dry skillet for 3–5 minutes, stirring. Cool and chop finely.

4. Assemble the cake

1. Level cake layers if needed. Place the first layer on your serving plate or turntable.
2. Lightly brush or sprinkle about 1 tbsp milk (or a milk + simple syrup mix) over the layer to moisten but not soak.
3. Spread a generous layer of custard (about 1/3 of the custard) over the cake, leaving ~½ cm from the edge.
4. Arrange a single layer of banana slices (about half the bananas) over the custard, then sprinkle some toasted chopped walnuts.
5. Repeat with the next layer(s). Finish by covering top and sides with remaining custard or whipped cream.
6. Decorate with banana slices, walnut halves, toasted coconut or chocolate shavings. Chill for at least 3 hours (overnight is best) to let the custard firm and the flavors meld.

Serving & presentation ideas

• For a clean look, pipe a border of whipped cream rosettes and place walnut halves and banana slices between rosettes.
• Dust the top lightly with cocoa powder or cinnamon for warmth.
• Serve chilled or at cool room temperature. For the best slice, chill 4+ hours so the custard sets completely.

Chef tips from the pros

Gordon Ramsay

“When you’re building layers, keep moisture under control — a thin brush of milk or syrup is fine, but too much will make the custard leak.”

Ina Garten

“Quality vanilla and ripe bananas will lift the cake — simple ingredients done well beats complexity.”

Bobby Flay

“Toast the nuts and save a few for the top — crunch is the texture that makes this cake sing.”

Substitutions & variations

• Egg-free sponge: Use a reliable egg-replacer sponge formula or make a two-layer oil-based cake using 1½ cups AP flour, 1 cup sugar, 1 cup milk, ½ cup oil, 1½ tsp baking powder, bake as directed.
• Gluten-free: Use a cup-for-cup gluten-free blend and add ¼ tsp xanthan gum if your blend lacks it. Texture will differ slightly.
• Nut-free: Omit walnuts and replace with toasted sunflower seeds or crushed graham crumbs for crunch.
• Tropical twist: Add a layer of sliced strawberries or thinly sliced kiwi with the bananas for color and acidity.
• Chocolate banana: Fold 2–3 tbsp cocoa powder into ¼ cup of the flour and swirl into one layer for a marbled effect.

Health tips & safety considerations

• Allergens: Contains eggs, dairy, wheat, and tree nuts (walnuts). Label clearly if serving guests with allergies.
• Custard safety: The custard contains cooked egg yolk and should be chilled promptly. Keep refrigerated and consume within 2–3 days.
• Banana oxidation: Bananas brown when exposed to air. To slow browning, brush banana slices lightly with a little lemon juice (diluted 1:4 with water) before layering; this also adds brightness.
• Storage temp: Keep the assembled cake refrigerated at ≤4°C / ≤40°F.

Nutrition & ingredient benefits (approximate, per whole cake and per slice)

Estimated values — will vary by exact brands and portion sizes. Calculated for entire cake using ingredients listed (no optional whipped cream) and divided into 12 slices.

Notes: Adding whipped cream, additional sugar, chocolate, or butter-based frosting will raise calories. Walnuts contribute heart-healthy fats; bananas add fiber and potassium. For lower sugar, reduce sugar by up to 20% and rely on ripe bananas for sweetness, but custard texture may be impacted slightly.

Storage, make-ahead & freezing

• Assembled cake: Refrigerate and consume within 2–3 days for best texture and safety.
• Make-ahead: Bake sponge layers and wrap tightly; keep custard chilled separately up to 2 days. Assemble on the day of serving for best texture.
• Freeze: Sponge layers freeze well individually (wrapped) up to 2 months. Custard does not freeze well. For frozen make-ahead, freeze layers and assemble with fresh custard on thawing day.
• Transport: Chill thoroughly before transporting; pack with cold packs to keep custard stable in warm weather.

Troubleshooting — common issues & fixes

Soggy layers after assembly

Too much milk or syrup used to moisten layers, or overly ripe bananas leaking juices. Use a light brush of milk or a 1:2 simple syrup (1 part sugar to 2 parts water) sparingly. Pat banana slices dry and optionally toss briefly with lemon juice to slow browning and reduce juice.

Custard lumps

If custard lumps form, press through a fine sieve or blend briefly with an immersion blender off heat. Proper tempering (whisking hot milk into yolk slowly) helps prevent curdling.

Cake sinks in the center

Underbaking, opening the oven early, or too much leavening can cause sinking. Bake until a toothpick shows moist crumbs and avoid opening the oven for at least 20 minutes during baking.

10 Detailed FAQs

1. Can I make this cake ahead? Yes — bake layers up to 2 days ahead and store wrapped; make custard the day before and assemble on serving day for the freshest texture.
2. How do I keep banana slices from browning? Lightly brush or toss slices with lemon juice diluted 1:4 with water. Use just enough to prevent browning without adding noticeable tartness.
3. Can I use store-bought custard or pastry cream? Yes — a high-quality store custard can work. Adjust sweetness and texture (fold in whipped cream if the custard is very thick).
4. What if I don’t want to use raw egg yolk? The custard here is cooked, so yolk is safe when cooked to thickened temperature. If you must avoid egg entirely, make a cornstarch-thickened vanilla cream without yolk (longer cook needed) or use an egg-free instant pudding mix (texture differs).
5. How ripe should the bananas be? Ripe with brown speckles — sweet and fragrant. Overripe very soft bananas will be sweeter but may leak more juice.
6. Can I replace walnuts with another nut? Yes — pecans or hazelnuts are great. To be nut-free, try toasted oat crumble or toasted coconut for crunch.
7. Is the cake freezer-friendly once assembled? Not recommended — the custard filling can change texture when frozen and thawed. Freeze unfrosted layers instead.
8. How do I get even layers? Use a kitchen scale to divide batter equally between pans and level with a spatula. If you only have one pan, cool and slice the baked cake horizontally.
9. Can I use whipped cream instead of custard? You can, but whipped cream alone is lighter and less stable; consider stabilizing the whipped cream with a small amount of mascarpone or gelatin (if keeping for longer than a few hours).
10. What’s the best way to slice clean pieces? Chill the cake for at least 1 hour, use a serrated knife warmed under hot water and wiped dry between cuts for cleaner slices.

Variations & celebration ideas

• Banana & caramel: Drizzle a thin layer of salted caramel between layers for a luxe touch.
• Tropical: Add a layer of crushed pineapple (drained) or mango slices with bananas.
• Birthday cake: Tint some of the whipped cream a pale pastel and pipe rosettes for a festive finish.

Related recipes & internal links

• Banana bread and banana desserts 🍌
• How to make and use pastry cream (custard) like a pro
• Toasting nuts: tips for maximum flavor 🌰
• Simple cake decorating ideas for home bakers

Final notes — why you’ll love this cake

This Banana Walnut Layer Cake balances comfort and refinement: an approachable sponge, home-style custard, ripe banana fruitiness, and toasty walnut crunch. It’s forgiving to make, scalable for parties, and can be dressed up or kept simple. Chill thoroughly before serving for clean slices and the best flavor melding. Share with friends, pair with tea or coffee, and enjoy the mix of textures and flavors that make every bite satisfying. 🍰🌰