Preheat the oven to 350°F. Grease, flour, and line the bottom of four 6-inch cake pans with parchment paper.

Using a handheld or stand mixer fitted with the paddle attachment, beat the butter and sugar on high speed until light and fluffy.

Next, add the eggs and vanilla, and mix until fully combined. Scrape down the sides of the bowl as needed.

In a medium bowl, whisk together the flour, baking soda, and salt.

Add the dry ingredients to the wet ingredients, alternating with the buttermilk.

Lastly, mix in the mashed bananas until everything is well combined.

Divide the batter evenly among the prepared cake pans. Bake for 40-45 minutes, or until a toothpick or cake tester inserted into the center comes out with just a few crumbs.

Allow the cakes to cool in the pans on a wire rack for 10 minutes. Afterward, flip the pans over and let them cool completely upside down.

In a microwave-safe dish or measuring cup, melt the salted caramel chips and heavy cream. Microwave in 15-second increments, stirring in between to prevent the mixture from seizing. Once smooth with no clumps, set aside to cool slightly.

Using a handheld or stand mixer fitted with the paddle attachment, beat the butter until fluffy. Add the slightly cooled ganache to the butter and beat until smooth.

With the mixer on low, gradually add the powdered sugar one cup at a time. Once all the powdered sugar is incorporated, increase the speed to high and whip for 3-5 minutes until the mixture is light and fluffy.

In a microwave-safe dish or measuring cup, melt the salted caramel chips and heavy cream. Microwave in 15-second increments, stirring in between to prevent the mixture from seizing. Once smooth with no clumps, set aside.

Level off the tops of the cake layers, if necessary, using a serrated knife or cake leveller.

Spread a small amount of buttercream on the base of your cake plate or board to help hold the cake in place. Place the first cake layer down. Spread about 1/2 cup of buttercream over the first layer and top with about 1/4 cup of toffee bits.

Place the second cake layer on top and repeat the process with buttercream and toffee bits. Do the same for the third layer.

Place the fourth cake layer on top, with the top side facing down.

Cover the entire cake with buttercream, smoothing the sides as necessary.

Once the cake is evenly covered, chill it for 10 minutes in the freezer or 20 minutes in the fridge.

If the ganache has cooled, gently warm it in the microwave in 10-second increments to prevent seizing.

You can either use a squeeze bottle or spoon the ganache onto the cake. Apply a bit at the edge of the cake to let it drip down, repeating this all around the cake. Pour the remaining ganache onto the center of the top of the cake and spread evenly.

Decorate the cake with the remaining buttercream and toffee bits as desired!