Preheat the oven to 200°C and line a Swiss roll tin with parchment.
Cream butter and icing sugar, beat in egg whites, fold in flour, liquorice essence, and food coloring.
Pipe black diagonal lines across the tin and refrigerate.
Whisk eggs and caster sugar until light, frothy, and leaving a trail.
Sift flour over the mixture and gently fold it in.
Pour batter into the tin and bake for 10-12 minutes until golden-brown.
Turn sponge onto sugared parchment and flip so black lines are on the bottom.
Beat filling ingredients until smooth and spread over cooled sponge.
Spread jam over buttercream, score a line 2cm from edge, and roll firmly.