Preheat oven to 350 F. Cream together butter and sugar. Add beaten egg yolks and milk. Sift dry ingredients together and add to mixture. Pour into one greased round cake pan. Bake until done, approximately 25 minutes. Meanwhile, mix filling ingredients together in double boiler and cook until thick. Cool slightly and spread on baked cake. For topping, beat 4 egg whites in double boiler until stiff. Add 1 cup sugar slowly, then add cinnamon. Fold in nuts. Spread over filling and bake at 350 F until topping is golden brown.