WALNUT DREAM CAKE WITH CUSTARD FILLING

1 pkg. (18 oz.) white cake mix
1/2 c. cornstarch
1/2 c. firmly packed brown sugar
3 egg whites
1 c. water
1/2 c. Hellmanns mayonnaise
1 c. finely chopped walnuts

CUSTARD FILLING AND WHIPPED TOPPING:

1 c. whipped heavy cream or Cool Whip

CUSTARD: In 1 quart saucepan mix 1/4 cup sugar and 3 tablespoons cornstarch. Gradually stir in 2 cups milk until smooth. Add 3 slightly beaten egg yolks, stirring constantly. Bring to a boil over medium-low heat and boil 1 minute. Remove from heat, stir in 1 teaspoon vanilla. cover surface with wrap. Refrigerate until cool.

CAKE: Grease and flour two 9 inch round cake pans. In large bowl with mixer at medium speed beat first 7 ingredients until well mixed. Pour into pans an bake at 375 degrees for 25 to 30 minutes or until tester inserted in center comes out clean. Remove. Cool on wire rack, split each layer horizontally. Fill with custard filling. Frost with whipped cream or Cool Whip.