Cassis Biscuit Roulade

Line a 40 x 30 cm rectangular baking tray with baking paper and lightly butter the paper. In the large bowl of the standing mixer, whip the egg whites and water at medium speed until frothy. Add the white vinegar, increase the speed to high, and continue beating until the whites form soft peaks. Add sugar, 1 tablespoon at a time, whip until they form stiff peaks.

Let the cake rest in the tray for 1 minute. Flip it out onto a clean tea towel that was sprinkled with powdered sugar. Brush the paper lining with water and let soak 1 minute before peeling it off the cake. Trim dry edges from the cake if needed. Roll the cake up tightly with the towel, rolling away from you and cool on a rack 30 minutes or more.