Cooking : Butternut Squash Layer Cake

Ingredients
1/2 cup butter, softened
1 cup sugar
1 cup packed brown sugar
1 cup mashed, cooked butternut squash
1 teaspoon maple flavoring
3 cups cake flour
4 teaspoons baking powder
1/4 teaspoon baking soda
1/2 cup milk
1 cup chopped walnuts
BROWN SUGAR FROSTING:
1 1/2 cups packed brown sugar
3 egg whites
6 tablespoons water
1/4 teaspoon cream of tartar
1/8 teaspoon salt
1 teaspoon vanilla extract

Directions
In a mixing bowl, cream the butter and sugars. Add eggs, one at a time, beating well after each addition. Add squash and maple flavoring; mix well. Combine flour, baking powder and baking soda; add to creamed mixture alternately with milk. Stir in walnuts. Pour into two greased and floured 9-in. round baking pans.
Bake at 350 degrees F for 25-30 minutes or until a toothpick inserted near the center comes out clean. Cool 10 minutes before removing from pans to wire racks.
For frosting, combine the brown sugar, egg whites, water, cream of tartar and salt in a heavy saucepan. With a portable mixer, beat on low speed for 1 minute. Continue beating over low heat until a thermometer reads 160 degrees F, about 8-10 minutes.
Pour frosting into a large mixing bowl; add vanilla. Beat on high speed until stiff peaks form, about 3 minutes. Spread between layers and over top and sides of cake.