Banana Cake

1. Preheat and Prepare Pans: Heat the oven to 350°F. Grease three 8-inch round cake pans and line the bottoms with parchment paper.
2. Mix Dry Ingredients: In a bowl, combine flour, baking soda, baking powder, cinnamon, and salt.
3. Cream Butter and Sugars: In a mixer, beat butter, oil, granulated sugar, and brown sugar for 4 minutes until fluffy.
4. Add Eggs: Beat in the eggs one at a time, fully mixing each before adding the next.
5. Add Flavors: Mix in the vanilla, then the sour cream and mashed bananas.
6. Combine Wet and Dry: Add half the dry mixture, then the buttermilk, followed by the rest of the dry ingredients. Mix just until combined.
7. Bake: Divide the batter between the pans and bake for 25 minutes, or until a toothpick comes out clean. Cool for 10 minutes, then transfer to a cooling rack. Let cool completely before frosting.

Dulce de Leche Frosting

1. Beat Butter and Cream Cheese: Mix the butter and cream cheese until fluffy, about 4 minutes.
2. Add Dulce de Leche: Beat in the dulce de leche.
3. Incorporate Sugar and Vanilla: Gradually add powdered sugar and vanilla, beating until smooth. Adjust with milk or cream for consistency.

Assemble the Cake

1. First Layer: Place one cake layer on a plate or turntable. Pipe a ring of frosting around the edge.
2. Add Filling: Spread ½ cup of dulce de leche in the center, then top with sliced bananas. Spread a bit more frosting on top.
3. Repeat: Add the next layer and repeat the frosting and filling process.
4. Top Layer: Add the final layer, then apply a crumb coat (thin layer of frosting) around the cake. Chill for 20 minutes.
5. Final Frosting: Frost the entire cake with the remaining frosting and decorate with dulce de leche, banana slices, caramel crispearls, or crumbled Biscoff cookies.

Storage

1. Refrigerate: Store the cake in the fridge for up to 3 days. Keep it covered once cut.
2. Freeze: Freeze slices for up to 2 months. Wrap in plastic and place in an airtight container.