1.Preheat oven to 180°C/160°C fan forced. Grease and line a 30cm x 25cm (base measurement) Swiss roll pan with baking paper, extending paper at long sides for handles.
2.Using an electric mixer, beat eggs and 1/2 cup sugar in a small bowl until thick and creamy. Sift flour 3 times onto baking paper, then gently fold into egg mixture with combined milk and butter. Spread mixture evenly into prepared pan. Bake for 10-12 minutes or until springy to the touch.
3.Place a piece of baking paper, cut slightly larger than the pan on work surface; sprinkle evenly with extra sugar. Turn sponge onto paper immediately; peel away lining paper. Trim crusty sides from sponge. Cover with a clean tea-towel, then, using your hand, press to flatten slightly. Cool.
4.Cut sponge and baking paper underneath sponge in half crosswise to make 2 pieces. Spread jam over sponge pieces. Using paper as a guide. roll each sponge tightly from long side. Cut each sponge roll into 6 mini rolls. Serve.
Try apricot jam or lemon curd instead of strawberry jam. Rolls will keep in an airtight container for up to 3 days.Note