Marbled Mayonnaise Cake

Preheat oven to 350F. Grease 2 9" pans. Line bottoms with waxed paper; grease paper. Dust pans with flour, tap out excess. In a large mixing bowl, beat together eggs, sugar and vanilla with an electric mixer on high until light and fluffy, about 3 minutes. Reduce speed to low and beat in mayonnaise. Sift together flour,baking soda, baking powder and salt. On low speed alternately add flour mixture and milk to mayonnaise mixture beginning and ending with flour and beat just until blended. In a small bowl whisk together cocoa and hot water until smooth. With a rubber spatula fold in 1 cup yellow batter to blend. Turn remaining yellow batter into prepared pans then pour 3 pools of chocolate batter on top of each pan. With a small spatula of knife, cut through batters to marbleize. Bake 30-35 minutes or until a cake tester inserted in center comes out clean. Let cakes cool in pans 10 minutes then unmold onto wire racks and remove wax paper. Invert cakes again and let cool completely. Fill and frost cake. Frosting 5 (1 ounce) squares unsweetened chocolate, cut into small pieces 6 Tbsp unsalted butter, cut up 2 cups sifted powdered sugar Pinch of salt 1 tsp. vanilla extract 1/2 cup heavy cream In a medium glass bowl, combine chocolate and butter. Microwave on medium 2 1/2-3 minutes or until butter is melted. Whisk butter and chocolate together until completely smooth. Transfer chocolate mixture to a large bowl. Let cool slightly, about 10 minutes. Beat chocolate mixture, 1 cup powdered sugar, salt and vanilla with an electric mixer on medium speed until light and fluffy. Beat in cream, then the remaining 1 cup powdered sugar until smooth and frosting is a spreadable consistency, about 1 minute longer. Fill and frost cake. Jan