Combine coffee, water, and sugar in a medium saucepan. Bring to a boil, and cook 5 minutes; set aside to cool.
Cream butter in a large mixing bowl. Beat egg yolks until thick and lemon colored; add to butter, mixing well.
Combine flour, baking powder, and salt; sift together 4 times. Add to creamed mixture alternately with coffee mixture, beginning and ending with flour mixture; mix well after each addition. Add vanilla, mixing well.
Beat egg whites (at room temperature) until stiff but not dry; fold into batter.
Pour batter into 2 greased 9- inch round cake pans. Sprinkle liberally with Crumb Topping. Bake at 400° for 30 minutes or until a wooden pick inserted in center comes out clean. Serve warm.