Step 1: Prepare the Chocolate Sponge Cake
Preheat the oven to 350°F (175°C). Line a jelly roll pan with parchment paper and lightly grease it.
In a bowl, sift together the flour, cocoa powder, baking powder, and salt.
In a separate large bowl, beat the eggs and granulated sugar using an electric mixer on high speed until the mixture becomes pale and fluffy (about 3–5 minutes).
Gently fold the dry ingredients into the egg mixture in three additions, alternating with the milk and oil. Add the vanilla extract and mix just until combined.
Pour the batter into the prepared pan, spreading it evenly. Bake for 10–12 minutes, or until the cake springs back when lightly touched.
Remove from the oven and let the cake cool for 5 minutes. While still warm, carefully roll the cake (with parchment paper) into a log. Let it cool completely.
Step 2: Make the Cherry Filling
In a small saucepan, combine the cherries, sugar, cornstarch, and water. Cook over medium heat, stirring constantly, until the mixture thickens and the cherries are soft.
Remove from heat and let the cherry filling cool completely.
Step 3: Whip the Cream
In a chilled bowl, beat the heavy cream, powdered sugar, and vanilla extract on high speed until stiff peaks form.
Step 4: Assemble the Roll Cake
Gently unroll the cooled cake and spread a thin layer of whipped cream over the surface, leaving a 1-inch border around the edges.
Spread the cooled cherry filling over the whipped cream.
Carefully roll the cake back up, using the parchment paper to guide you. Place the roll seam-side down on a serving plate.
Step 5: Garnish and Serve
Spread the remaining whipped cream over the roll cake. Garnish with fresh cherries and chocolate shavings.
Refrigerate for at least 1 hour before slicing and serving.
