Hazelnut Chiffon Cake with Mocha Buttercream

Makes 12 servings. To toast hazelnuts, spread in a single layer in shallow baking pan; toast at 375 F for 5-10 minutes, shaking pan once or twice. To remove skins, rub nuts while still warm, between palms of hands or in a kitchen towel. In large bowl, combine flour, sugar, nuts, baking soda and salt. Add water, oil, egg yolks and vanilla; beat until smooth. Using electric mixer on high speed, beat egg whites and cream of tartar until stiff peaks form. Gently stir 1/3 of beaten egg whites into batter; gradually fold remaining egg whites into lightened batter. Pour into ungreased 10-cup angel food pan. Bake at 325 F for 1 1/4 hours or until top of cake springs back when touched. Remove cake from oven and immediately invert onto glass bottle or metal funnel. Cool completely. Remove cake from pan; frost top and sides with Mocha Buttercream. Mocha Buttercream: Using electric mixer, beat 3/4 cup (1-1/2 sticks) butter, softened, until light. beat in 1-1/2 cup sifted powdered sugar, 2 T unsweetened cocoa powder and 1 tsp pure vanilla extract. Add 2 to 3 T strong brewed coffee, beating until very light and of spreading consistency.