Preparing the Chocolate Sponge Cake

1. Preheat the Oven: Set your oven to 350°F (175°C). Line a 10×15-inch jelly roll pan with parchment paper.
2. Whisk the Eggs and Sugar: In a mixing bowl, beat the eggs and sugar with an electric mixer until pale and fluffy, about 5 minutes. Mix in the vanilla extract.
3. Combine Dry Ingredients: Sift together the flour, cocoa powder, baking powder, and salt in a separate bowl. Gradually fold this mixture into the egg mixture, ensuring it’s fully combined but not overmixed.
4. Bake the Sponge: Pour the batter evenly into the prepared pan. Bake for 10-12 minutes, or until the cake springs back when touched.
5. Roll the Cake: Dust a clean kitchen towel with powdered sugar. While the cake is still warm, turn it out onto the towel, peel off the parchment, and gently roll the cake with the towel from the short end. Let it cool completely.

Making the Cherry Filling

1. Prepare the Cherries: If using fresh cherries, combine them with cherry syrup, cornstarch, and lemon juice in a saucepan. Cook over medium heat until thickened. If using pie filling, gently heat it with the cherry syrup for a smoother consistency. Allow to cool.

Whipping the Cream Filling

1. Whip the Cream: Beat the cold heavy cream, powdered sugar, and vanilla extract together until stiff peaks form.

Assembling the Roulade

1. Unroll the Cake: Carefully unroll the cooled sponge. Spread a layer of whipped cream over the surface, followed by the cherry filling, leaving a small border around the edges.
2. Roll the Cake Again: Gently roll the cake back up without the towel. Place seam-side down on a serving plate.

Decorating the Roulade

1. Add Finishing Touches: Top the roulade with dollops of whipped cream, fresh cherries, chocolate shavings, and white chocolate curls, if desired. Dust with powdered sugar for a snowy effect.