Ingredients
Method
1.Preheat oven to 200C or 180C fan. Grease and line base and sides of a 25cm x 35cm Swiss roll pan.
2.Using an electric mixer, beat eggs, sugar and vanilla in a large bowl for 5-8 mins, until mixture is thick and creamy and a ribbon trail forms when beaters are lifted from mixture. Sift over flour, then drizzle in butter and treacle. Using a large metal spoon, fold together until mixture is just combined (do not over-mix). Pour mixture into prepared pan and smooth surface evenly. Bake for 10-12 mins, until sponge bounces back when lightly touched at centre.
3.Meanwhile, lay a large sheet of baking paper on a clean flat work surface and dust with 2 tbsp of extra sugar.
4.Turn out sponge onto prepared paper and carefully peel baking paper off (from top of sponge). Using baking paper underneath as a guide, roll up cake tightly from one long side to form a log. Cool.
5.Unroll cake, then spread with whipped cream and scatter over banana. Drizzle with extra treacle. Re-roll cake tightly, without baking paper, and carefully transfer to a serving platter, seam-side down. Dust with remaining extra sugar. Slice and serve.