In a large mixing bowl, thoroughly mix 1/2 cup flour, sugar, salt and undissolved yeast. Beat in butter or margarine. Gradually add water to dry ingredients; beat 2 minutes at medium speed of electric mixer, scraping bowl occasionally. Add egg and 1/2 cup flour or enough flour to make a thick batter. Beat at high speed 2 minutes, scraping bowl occasionally. Stir in remaining flour. Spread batter evenly into two greased 9-inch round pans or one 9-inch square pan. Cover with Topping.