Pre-heat oven to 350 degrees. Coat a 15x10x1 inch jelly-roll pan(or old time cookie sheet with sides) Line with wax paper and coat with cooking spray. Set aside.
2Beat egg yolks at medium speed with an electric mixer until thick and pale, add 1/2 cup sugar,beating well. Beat in buttermilk,vinegar and food coloring,.
3In small bowl,combine flour,cocoa,baking soda and salt, sift. Gradually add to egg mixture,beating until well blended..
4In a medium bowl,beat egg whites at medium-high speed with an electric mixer until foamy. Add 1/4 cup sugar, 1 Tablespoon at a time,beating until stiff peaks form. Fold eggs into chocolate mixture.
5Spread batter into prepared pan, Bake for 10-12 minutes, or until cake springs back when lightly touched in center.
6Shift 2 Tablespoons confectioner's sugar onto a 15x10x1 inch rectangle on clean dish towel. Immediately loosen cake from side of pan, and turn out onto prepared towel. Peel off wax paper. Sift remaining 2 Tablespoons of confectioner's sugar over cake. Starting at narrow end,roll up cake and towel together; place cake, sean side down,on wire rack. Cool cake completely.
7Gently unroll cake roll. Spread with cream cheese white chocolate filling. Reroll cake without the towel; place seam side down on serving platter. Dust cake with confectioner's sugar,if desired. Cut into 3/4" slices to serve.
8CREAM CHEESE WHITE CHOCOLATE FILLING:
In large bowl beat cream cheese and butter at medium speed with mixter until creamy. Beat in vanilla, Gradually beat in confectioner's sugar until smooth. Stir in white-chocolate morsels.