Step 1: Preheat and Prepare the Pans

Preheat your oven to 350°F (175°C). Grease two 8-inch round cake pans and lightly dust them with flour to ensure easy removal of the cake later. Set them aside.

Step 2: Mix the Dry Ingredients

In a medium-sized bowl, whisk together the all-purpose flour, baking soda, and salt until well combined. This ensures that the leavening agents are evenly distributed in the cake.

Step 3: Cream Butter and Sugar

In a large mixing bowl, use an electric mixer to cream the softened butter and granulated sugar until the mixture becomes light, fluffy, and pale in color. This process helps create a soft, airy texture for the cake.

Step 4: Add the Eggs and Vanilla

Add the eggs, one at a time, mixing well after each addition. Then, pour in the vanilla extract and mix until combined.

Step 5: Incorporate the Bananas and Sour Cream

Add the mashed bananas and sour cream to the wet mixture. Stir gently until the ingredients come together smoothly, creating a fragrant, silky batter.

Step 6: Combine Wet and Dry Ingredients

Gradually add the dry ingredients to the wet mixture, stirring until just combined. Avoid overmixing the batter to maintain a tender crumb.

Step 7: Fold in Walnuts and White Chocolate Chips

Gently fold the chopped walnuts and white chocolate chips into the batter to give it added texture and a hint of sweetness.

Step 8: Divide the Batter and Bake

Divide the batter evenly between the two prepared cake pans. Smooth the tops with a spatula for even baking.

Step 9: Bake the Cakes

Place the pans in the preheated oven and bake for 30-35 minutes. Insert a toothpick into the center of each cake to check for doneness—if it comes out clean, the cakes are ready.

Step 10: Cool the Cakes

Allow the cakes to cool in their pans for 10 minutes. Then, carefully transfer them to a wire rack to cool completely before adding the custard.

Step 11: Assemble the Cake

Once the cakes are fully cooled, place one layer on a serving plate. Spread half of the creamy custard on top. Place the second cake layer over the first, and smooth the remaining custard over the entire cake, covering the top and sides evenly.

Step 12: Garnish and Serve

For the finishing touch, garnish the cake with banana slices and sprinkle with whole or halved walnuts. You can serve the cake immediately or chill it in the refrigerator until you’re ready to enjoy.