Preheat the oven to 350°F (175°C) and line a jelly roll pan with parchment paper.
Prepare the sponge cake batter by mixing the eggs, sugar, flour, and dissolved instant coffee until light and smooth.
Spread the batter evenly into the prepared pan and bake for 10–12 minutes until the cake is lightly golden.
Turn the warm cake onto a clean kitchen towel dusted with powdered sugar and gently roll it up. Let it cool completely.
Unroll the cake and spread an even layer of mascarpone whipped cream filling.
Carefully roll the cake back into a tight log, dust with cocoa powder, and refrigerate for at least 1 hour.
Slice and serve chilled for the best flavor and texture.