Preheat the oven to 350 degrees F / 175 degrees C. Generously grease a 9 by 13-inch (24 by 36cm) cake pan (or three 8-inch by 20cm cake pans), then line it with greased parchment paper.

In a separate bowl, whisk together the mashed bananas, oil, vanilla, and eggs.

In another bowl, using a whisk, whip the heavy cream to medium peaks. Using a rubber spatula, fold the whipped cream into the batter, then fold in the walnuts (if using).

Pour the batter into the prepared pan and spread evenly using a small offset spatula. Gently tap the pan on the counter several times to release excess air bubbles.

Bake until a tester comes out clean, 40 to 45 minutes (about 30 minutes for 8-inch rounds). Let the cake cool completely before removing it from the pan, then invert it t onto a serving platter.

Take twelve small pieces of the marzipan and roll between your fingers, until they are a 1/2-inch (1.3cm) long narrow cylinder or capsule shape. Taper one end slightly to become the back of the bee.

Using a food-safe paintbrush or a toothpick and black food coloring, paint stripes on the marzipan. Let the stripes dry. Then, using a small, clean paintbrush, paint. gold luster dust between the black stripes.

Press the sliced almonds into the sides of the marzipan to create the bees' wings. Put the finished bees on a toothpick and set them aside.

In a food processor fitted with the metal blade, pulverize the praline until there are small bits about the size of pine nuts or smaller-but not as fine as powder.

In two separate bowls, divide the buttercream in half and add the praline to one batch and stir a few drops of yellow food coloring into the other.

Using an offset spatula, spread half of the praline buttercream over the cake, making sure it goes all the way to the edge. Place the second cake round over the frosting and spread with the remaining praline buttercream. Top with the cake baked in the bowl (trim the bottom flat) as the final layer.

If desired, at this point, you could crumb-coat the cake with some of the yellow buttercream.

Put a thick layer of yellow buttercream over the cake. Using a small icing spatula, and starting at the top of the cake, create a spiral by slowly spinning the cake turner and moving the spatula downward.

Place the bees' toothpick into the cake to create the illusion of bees buzzing around. Serve the cake immediately.

Line a baking sheet with lightly greased parchment paper or a silicone mat.

In a medium saucepan over high heat, combine the sugar, water, and corn syrup and let melt, without stirring.

Allow the mixture to boil until the sugar just starts to turn amber along the edge. You can now stir without fear of crystalizing.

When the caramel is evenly deep amber throughout and just starting to smoke, turn off the heat and stir in the pecans and salt. Immediately pour the nut mixture in a thin layer onto the prepared baking sheet.

Let the mixture cool completely, then transfer to a food processor and pulse until the praline is pulverized and there are no pieces larger than a pine nut.

Transfer the praline in an airtight container and store in a cool, dry spot for up to 3 days.

In the bowl of a stand mixer, combine the honey and egg whites.

Put 1 inch (2.5cm) of water in the bottom of a double boiler or a medium saucepan and bring to a gentle simmer over medium-low heat. Place the bowl with the egg mixture over the simmering water and stir the mixture with a rubber spatula until melted (140 degrees F / 60 degrees C) and thin.

Place the bowl in the stand mixer fitted with the whisk attachment and beat on medium-high speed until the egg foam is light, fluffy, and glossy and the bowl feels just about room temperature. (If the egg foam isn't cooled sufficiently, the butter will melt when you add it.)

Once the egg foam is whipped and cooled, turn the mixer speed to medium, add the butter, 2 Tbsp at a time, and beat until incorporated. Once you have finished adding the butter and it has mixed for about 1 minute, the buttercream will be creamy and glossy looking again. Turn the speed to low; add the espresso (if using), vanilla, and salt; and mix until well blended.

Use immediately or transfer to an airtight container and store in the refrigerator for up to 7 days or in the freezer for up to 1 month.