Snickers Cake

Preheat oven to 350 °F. Grease three 8-inch-diameter cake pans with 1 1/2-inch-high sides. Line bottoms with waxed paper. Melt chocolate in top of double boiler over simmering water; stir until smooth. Remove from over water and cool to barely lukewarm. Using electric mixer, cream butter in large bowl until light and fluffy. Gradually add 1 1/4 cups sugar, beating until smooth. Beat in egg yolks 1 at a time. Mix in vanilla. Stir in chocolate, then peanuts. Sift flour over batter and gently fold in. (Batter will be very thick.) Using clean dry beaters, beat whites with cream of tartar in another large bowl to soft peaks. Gradually add remaining 1/4 cup sugar and beat until stiff but not dry. Fold 1/2 of whites into batter to lighten. Gently fold in remaining whites. Divide batter among prepared pans. Bake until tester inserted in centers comes out clean and tops are crusty, 25 to 30 minutes. Cool in pans on racks 10 minutes. Run small sharp knife around pan sides to loosen, if necessary. Turn out onto racks. Peel off paper. Cool to room temperature. (Cakes can be prepared 2 days ahead. Wrap tightly and refrigerate.)