Step 1: Prepare the Banana Sponge Cake

1. Preheat the oven: Preheat your oven to 375°F (190°C). Line a 10×15-inch jelly roll pan with parchment paper, ensuring the edges are fully covered, and lightly grease the paper.
2. Beat the eggs and sugar: In a large bowl, beat the eggs and granulated sugar with a hand or stand mixer on high speed for 3–4 minutes, or until the mixture is pale, thick, and triples in volume. This step is essential for creating a light and airy cake.
3. Add vanilla and bananas: Gently mix in the vanilla extract and mashed bananas until just combined.
4. Sift the dry ingredients: In a separate bowl, sift together the flour, baking powder, baking soda, and salt. Gradually fold the dry ingredients into the wet mixture using a spatula. Be careful not to overmix to preserve the batter’s lightness.
5. Bake the cake: Pour the batter into the prepared pan and spread it evenly with an offset spatula. Bake for 10–12 minutes, or until the cake springs back when touched and a toothpick inserted into the center comes out clean.

Step 2: Roll the Cake While Warm

1. Dust a towel: Lay a clean kitchen towel on a flat surface and generously dust it with powdered sugar. This prevents the cake from sticking.
2. Invert the cake: While the cake is still warm, carefully invert it onto the prepared towel. Gently peel off the parchment paper.
3. Roll the cake: Starting at the short end, roll the cake and towel together into a tight spiral. Allow the rolled cake to cool completely on a wire rack for about 1 hour. Rolling the cake while warm helps it retain its shape without cracking.

Step 3: Make the Caramel Cream Filling

1. Whip the cream: In a chilled mixing bowl, beat the cold heavy cream, powdered sugar, and vanilla extract on medium-high speed until stiff peaks form.
2. Fold in the caramel: Gently fold the caramel sauce into the whipped cream until fully incorporated. Be careful not to deflate the whipped cream.

Step 4: Assemble the Roll Cake

1. Unroll the cake: Once the cake is completely cool, carefully unroll it. Spread an even layer of the caramel cream filling over the surface, leaving a 1/2-inch border around the edges.
2. Re-roll the cake: Gently roll the cake back up (without the towel) into a tight spiral. Transfer the roll seam-side down to a serving plate.
3. Chill the cake: Refrigerate the roll cake for at least 30 minutes to set the filling and make slicing easier.

Step 5: Garnish and Serve

1. Drizzle with caramel: Just before serving, drizzle the cake with additional caramel sauce.
2. Add optional toppings: Garnish with chopped nuts, banana slices, or a dollop of whipped cream for an extra-special touch.
3. Slice and serve: Use a sharp knife to slice the roll cake into even portions. Enjoy!