Step 1

Using a large metal spoon, gently fold a third of the whites into the cocoa mix  to loosen. Fold in remaining whites until combined – be careful not to knock out too much air. Spoon into the prepared tin and level gently. Bake for 20min until the cake feels springy to the touch. Lay out a piece of baking parchment dusted generously with cocoa powder. Invert cake on to parchment and peel away paper from sponge. Leave to cool on a wire rack.

Step 2

For the filling, whisk cream until it just holds its shape. Coarsely grate the white chocolate and fold into cream with the vanilla bean paste.