Learn how to make a banana split cake from vanilla sponge cake stacked with chocolate fudge sauce, banana compote, and peanut crunch with this layer cake recipe.
Combine unsalted butter, granulated sugar, and light brown sugar in the bowl of a freestanding electric mixer with a paddle attachment. Cream together on medium-high speed for 2 to 3 minutes.
Use a rubber spatula to scrape down the sides of the bowl. Mix in the eggs, one at a time, then increase speed and mix on medium–high again for 2 to 3 minutes. Scrape down the sides of the bowl once more.
On low speed, stream in buttermilk, oil, and vanilla. Continue mixing for 4 to 6 minutes, until the mixture is practically white, twice the size of your original fluffy butter-and-sugar mixture, and completely homogenous. Be patient and don't rush the process! It takes a long time to force so much liquid into an already fatty mixture that doesn't want to make room for the liquid.
Stop the mixer and use a rubber spatula to scrape down the sides of the bowl.
With the mixture on low speed, add cake flour, baking powder, and kosher salt. Mix for 45 to 60 seconds, just until your batter comes together and any remnants of dry ingredients have been incorporated. BE CAREFUL NOT TO OVERMIX. Use a rubber spatula to scrape down the sides of the bowl — if you see any lumps of cake flour in there while you're scraping, mix for another 45 seconds.
Prepare a quarter sheet pan by generously spraying with cooking oil and line with parchment. Lightly spray the parchment as well.
Using a rubber spatula, transfer the cake batter to the sheet pan, spreading the cake batter in an even layer in the pan. Give the bottom of your sheet pan a tap on the countertop to even out the layer.
Bake the cake for 30 to 35 minutes. The cake will rise and puff, doubling in size, but will remain buttery and dense. At 30 minutes, gently poke the edge of the cake with your finger: the cake should bounce back slightly and the center should no longer be jiggly. Leave the cake in the oven for an extra 3 to 5 minutes if it doesn’t pass these tests.
Take the cake out of the oven and cool on a wire cooling rack. The cooled cake can be stored in the fridge, wrapped in plastic wrap, for up to 5 days.
Chocolate fudge sauce
Combine the chocolate, cocoa powder, and salt in medium bowl.
Combine the glucose, molasses, sugar, and heavy cream in a heavy-bottomed saucepan and stir intermittently while bringing to a boil over high heat. The moment it boils, pour it into the bowl holding the chocolate. Let sit for 1 full minute.
Slowly, slowly begin to whisk the mixture. then continue, increasingly the vigour of your whisking every 30 seconds, until the mixture is glossy and silky-smooth. This will take 2 to 4 minutes, depending on your speed and strength. You can use this sauce at this point or store it in an airtight container in the fridge for up to 2 weeks.
Peanut crunch
Purée the chopped roasted peanuts with the oil, brown sugar, and salt in a food processor until it's the consistency of wet sand.
Transfer to a bowl and stir in the pailleté feuilletine (or crushed Gavottes cookies). Store in an airtight container at room temperature for 5 days or in the fridge for up to 2 weeks.
Cherry frosting
In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter and icing sugar for 5 minutes on medium–high until very light and fluffy.
Grind the freeze-dried cherries and strawberries together in a food processor until you get a fine powder.
Add the powder to the frosting, and stir on low to combine. Use the frosting immediately.
Banana compote
In a non-stick fry pan, melt the butter. Add the brown sugar and sliced bananas and stir.
Bring the mixture up to a simmer, and continue cooking for about 10 minutes, stirring every so often, until the bananas are soft, but still hold their shape. The goal is to form a chunky compote while removing some of the moisture from the bananas.
Soak
Combine the juice with the maraschino cherry syrup. Stir well to mix them together. Use immediately.
To assemble
Prepare a 6-inch (15.25 cm) cake ring (from Amazon) by placing it on a parchment-lined rimmed baking sheet, lining the inside of the ring with a 20-inch (50.8 cm) long piece of acetate (also on Amazon).
Cut out two 6-inch (15.25 cm) circles of cake, and two half circles. Fit the two half circles of cake at the bottom of the acetate-lined ring, filling any gaps with the leftover cake scraps.
Brush the cake with half the soak (~30 grams), then smooth on half of banana compote (roughly ⅔ cup).
Sprinkle one third of the peanut crunch over the compote. Dollop with half of the warmed chocolate fudge sauce frosting, then gently spread into an even layer.
Gently fit a second strip of acetate between the first acetate strip and the ring to give your mold more height. Then, place the next layer of cake over the chocolate sauce, and repeat the previous step by brushing with soak, smoothing with compote, sprinkling with peanut crunch, then dolloping/smoothing with warm chocolate sauce.
Place the final layer over top, pressing slightly. Spread with the frosting and sprinkle with the rest of the crunch.
Freeze for a few hours to set, if not overnight.
On the day you are serving the cake, pop the frozen cake out of the ring, placing it on a cake stand. Pull off the strips of acetate and let the cake defrost for about 3–6 hours in the fridge before serving.
Notes
I highly recommend to use a kitchen scale to weigh out ingredients because the conversions for some to volume/cups is approximate, which is not ideal! Please weigh your ingredients!
If the fudge sauce is too thick to spread, microwave it for 30 seconds to loosen it up. I highly recommend this because otherwise, the fudge sauce will pull up the crunch layer and it will be hard to achieve the distinct layers we are looking for!
If you can't find pailleté feuilletine, you can replace it with crushed "Gavottes" which are a thin crispy rolled crêpe cookie from France, which we can find in grocery stores in Quebec. This is what I used to make the peanut crunch.
The banana compote may darken with time from the fruit's exposure to air. This is a natural browning process and nothing to worry about. A splash of lemon juice may help preserve the colour, temporarily.
For the dark chocolate, I used Cacao Barry Ocoa 70 % dark chocolate.