-macaroons), finely -ground For Cake: ========= Preheat oven to 375 F. Butter and flour 3 9-inch round cake pans. Beat yolks until they are pale yellow and form a ribbon when beaters are lifted, about 5 minutes. Beat in rum and vanilla. Beat whites with cream of tartar to soft peaks. Add sugar 1 tablespoon at a time and continue beating until stiff and shiny. Stir 12 ounces of semisweet chocolate and butter into yolks until well combined. Gently fold in 1/4 of egg whites to lighten the batter, then gently fold in the remaining whites. Sift together cornstarch and cocoa; combine with ground amaretti. Gently fold into the batter. Divide batter among prepared pans. Bake until centers of cakes rise and tops begin to crack, 18 to 20 minutes. Cool 10 minutes in pans, then cool completely on wire rack (cakes will fall slightly.)