In a large mixing bowl, beat egg yolks on high for 3 minutes or until light and fluffy. Gradually add sugar and vanilla, beating until thick and lemon-colored. Combine flour, cocoa and baking powder; gradually add to egg yolk mixture. Beat on low until well mixed (mixture will be thick). Beat egg whites and salt until soft peaks form. Fold a small amount into batter until no streaks of white remain; add the remaining egg whites. Grease a 15-in x 10-in x 1-in pan; line with waxed paper and grease and flour paper. Spread batter evenly in pan. Bake at 180ºC or 15 minutes or until cake springs back when lightly touched. Turn out onto a linen towl dusted with confectioners' sugar. Peel off paper and roll up with the towel. Cool for 30 minutes. Unroll cake; spread with ice cream to within 1 in. of edges. Roll up again (this time without the towel inside cake). Cover with plastic wrap and freeze until serving.

FOR THE CHOCOLATE SAUCE: In the top of a double boiler over hot water, melt chocolate and butter. Gradually add warm milk and sugar; stir constantly for 5 minutes or until completely dissolved. Spoon over slices of cake. YIELD: 1- half cups sauce