1. Stir together Kellogg's® Corn Flake Crumbs, flour, cocoa powder, soda and salt. Set aside.
2, In large mixing bowl, beat together sugar and mayonnaise until smooth. Stir in dry ingredients, mixing until combined. Add boiling water and vanilla, blending thoroughly. Pour into greased 13 x 9 x 2-inch baking pan.
3. Bake at 350° F about 35 minutes or until wooden pick inserted near center comes out clean. When cool, frost with Fluffy White Frosting.
4. To make frosting: Combine flour and small amount of the milk in small saucepan, mixing until smooth. Add remaining milk, stirring until combined. Cook over medium heat, stirring constantly, until bubbly and thickened. Cool completely.
5. In small electric mixer bowl, beat together margarine and sugar until light and fluffy. Add cooled milk mixture and vanilla, beating until smooth and no sugar granules remain.