Start by preheating your oven to 350°F (175°C). Grease a 15x10-inch Swiss roll tin and line it with parchment paper, ensuring it covers the edges for easy removal later.

In a large mixing bowl, whisk the eggs and granulated sugar together with an electric mixer for about 5–7 minutes, until the mixture is pale, thick, and fluffy. You’ll know it’s ready when it forms a ribbon trail.

In a separate bowl, sift together the cocoa powder, all-purpose flour, baking powder, and salt. Gently fold this dry mixture into the egg mixture, being careful to keep the air in the batter.

Pour the batter into the prepared tin and spread it out evenly. Bake for 10–12 minutes, or until the sponge is just set and springs back when lightly touched. Don’t overbake, as you want the sponge to stay soft and pliable.

Lay a clean sheet of parchment paper on your work surface and sprinkle it generously with sugar. Turn the warm sponge onto the sugared paper and peel off the baking parchment. Trim the edges if necessary, then roll the sponge tightly with the parchment. Let it cool completely in this rolled shape.

Melt the dark chocolate in a heatproof bowl set over a pan of simmering water, or use the microwave in short bursts. Let the chocolate cool slightly. Whip the heavy cream until soft peaks form, then gently fold the melted chocolate into the whipped cream.

Carefully unroll the cooled sponge and spread a thin layer of raspberry jam across the surface. Spread the chocolate cream evenly over the jam, leaving a small border around the edges. Gently roll the sponge back up without the parchment, keeping it tight but without squishing the filling.

Transfer the roulade to a serving plate and dust the top generously with cocoa powder. Chill in the fridge for at least 30 minutes to help it set before slicing and serving.