Prepare cake: preheat oven to 400 degrees. Grease a 15 x 10 x 1 inch jelly roll pan. Line bottom with waxed paper, grease paper. Sift together flour, baking powder and salt onto waxed paper
Beat egg whites in small bowl at high speed until soft peaks form. Beat in 1/4 cup granulated sugar, 1 TBS at a time until small peaks form.
Beat yolks and 1/4 cup sugar and vanilla in a small bowl until thick and fluffy. Fold in flour mixture, half at a time until completely blended
Fold meringue into egg yolk mixture until no streaks remain. Spread mixture evenly in prepared pan.
Bake at 400 degrees for 10 minutes or until center springs back when lightly pressed with fingertip.
Loosen cake around edges with knife, sieve 10 x sugar over cake. Cover with paper towel or kitchen towel. Invert onto wire rack, peel off waxed paper. Starting at short end roll up cake with towel. Cool cake completely on wire rack.
Prepare filling : wash and hull berries dry with paper towel. Slice into small bowl. Beat heavy cream in another bowl until slightly thickened. Add 10 x sugar. Continue beating until stiff.
To assemble : unroll cake carefully. Sprinkle top of cake evenly with sliced strawberries. Cover with whipped cream spread to within 1/2 inch of all edges. Retool cake again using towel as guide. Refrigerate until serving time.