Fresh blackberries, blueberries, and raspberries make the perfect filling for this white jelly roll cake. Serve with a few berries on the side to make this dessert extra special.
Heat oven to 350 degrees F.
In a small saucepan, stir together the sugar and cornstarch. Stir in berries and 1 tablespoon water and heat over medium heat. Cook 9 to 10 minutes, until thickened, bubbly and most of the berries have popped. Break up remaining berries with a spoon. Remove from heat; cool.
Coat a 15 x 10 x 1-inch jelly roll pan with nonstick cooking spray. Line bottom of pan with parchment or waxed paper. Spray paper. In a medium-size bowl, stir together the flour, baking powder and salt. In a large bowl, beat the eggs with an electric mixer for 5 minutes, until very light yellow. Add granulated sugar in batches, beating until smooth. Beat in vanilla extract.
Fold flour mixture into egg mixture until no lumps remain. Pour into prepared pan, spreading level. Bake at 350 degrees F for 12 to 14 minutes or until lightly browned.
Meanwhile, dust a clean kitchen towel with confectioners' sugar. When cake is done, turn out onto towel. Roll up towel and cake; cool completely.
Unroll cake; spread with filling. Roll up again, without the towel. Frosting: Transfer cake to a platter; spread with thawed whipped topping. Slice and serve.