Helen's Black Walnut Cake

This is another recipe that did not have any directions except for the most vaguest, which says, "Cook till thick", which I believe is for the filling. I will try my best to make this recipe work.
Helen's Black Walnut Cake

2 cups brown sugar
3/4 cup butter
2 eggs
1 cup sour cream
1 tsp. soda
1 tsp. cloves
1 Tbls. cinnamon
1/2 tsp. nutmeg
2 cups sifted flour with spices
1/2 cup black walnuts

Filling: 1 cup sugar
            2 eggs
            2 heaping Tbls. cornstarch
            1 cup black walnuts
            1 pint boiling milk

Sift flour with spices, as directed; set aside. cream brown sugar with room temperature butter until light and fluffy. Add eggs, beat well. Stir soda in with the sour cream and add to creamed mixture; blend well. Remove 1/4 cup of flour and blend with walnuts.  Add flour mixture to creamed mixture and blend well. Fold in walnut/flour mixture. Pour into two greased 8" or 9" pans. Bake at 350 degrees for 30 minutes, or till tests done with a toothpick.  Rmove from oven and allow to cool 10 minutes before turning out onto wire racks. Cool completely before adding cooled filling.
For filling: Scald milk. In top of double boiler combine sugar and cornstarch. Stir in milk and cook until thickened. Beat two eggs in a bowl and add a bit of the hot custard to temper the eggs and then add them to the milk mixture. Cook until incorporated and thickened. Remove from heat and allow to cool. Add black walnuts. Place between layers of cake.