All thanks and credit Lost Recipes Found at https://lostrecipesfound.com/german-chocolate-cake-marshall-fields/#more-455, where the site notes: “If there is a body of recipes Chicagoan’s miss most, it’s those from Marshall Field’s. So many people have written in search of this or that beloved dish. I’ve tracked down several of the recipes and done the math and tweaking to convert them from high-volume quantities to home-cook versions. This cake is a beautiful testament to just how good Marshall Field’s kitchen recipes were.”
Ingredients:
4 oz. Bakers German Sweet Chocolate
1/2 c. boiling water
2 1/2 c. sifted cake flour
1 t. baking soda
1/2 t. salt
1 c. butter or margarine
2 c. sugar
4 egg yolks, unbeaten
1 t. vanilla
1 c. buttermilk
4 egg whites, stiffly beaten
Topping/Filling:
2 c. butter
1 3/4 c. sugar
4 1/2 T. flour
8 egg yolks
2 c. evaporated milk
3 c. toasted pecans, chopped
4 c. flaked coconut

Instructions:
Melt chocolate in microwave at 50% power. Mix with boiling water. Cool.

Sift cake flour, soda and salt together. Cream margarine, sugar and vanilla until light and fluffy–about 3 min. at medium speed. Add egg yolks a little at a time, beating after each. Add melted chocolate. Blend. Add sifted dry ingredients alternately with buttermilk, starting with dry ingredients and blending after each addition. Mix 1 min. with medium speed mixer.

Beat egg whites until stiff, fold into batter. Pour into 4, greased 9″ cake pans. Bake 350 degrees for 24 to 35 min., or until done.

Frosting/filling: Melt butter. Add sugar and flour, whisking constantly until boiling. Add 1/4 of the evaporated milk to the egg yolks. Set aside. Add the rest of the milk to the butter mixture. Whisking constantly, heat to boiling. Add egg yolks/evaporated milk mixture, still whisking. Boil again. Press through sieve to remove any bits of cooked egg. Stir in pecans and coconut. Cool. Spread on and in-between layers of cake.