Place all ingredients except flavoring in top of double boiler (not over heat); beat 1 minute with electric mixer. Place over boiling water and cook, beating constantly until frosting forms stiff peaks, about 7 minutes (don't overcook). Remove from boiling water. Pour into mixing bowl and add maple, beat until of spreading consistency, about 2 minutes. Frosts tops and sides of 2 8 or 9-inch layers or one 10-inch tube. From Bh&G.