Grease a 15-x 10-x 1-inchjellyroll pan with vegetable oil, and line with waxed paper. Grease waxed paper with vegetable oil; set aside.
Beat egg yolks until thick and lemon colored; gradually add 1/2 cup sugar, beating constantly. Stir in hot water.
Beat egg whites (at room temperature) until foamy; gradually add remaining 1/2 cup sugar, beating until stiff but not dry. Fold yolk mixture into whites. Combine flour, baking powder and cocoa; gently fold into egg mixture.
Spread batter evenly in prepared pan. Bake at 400° for 15 minutes or until cake springs back when lightly touched.
Immediately loosen cake from sides of pan, and turn out onto a 15- x 10-inch linen towel. Peel off waxed paper. Starting at narrow end, roll up cake and towel together; cool on a wire rack, seam side down.
Beat whipping cream until foamy; gradually add 3 tablespoons sugar, beating until soft peaks form. Fold in vanilla.
Unroll cake and remove towel. Spread cake with whipped cream; reroll. Place on serving plate, seam side down. Spread Chocolate Frosting on cake; garnish with chopped pecans. Chill.