There appear to be a large variety of recipes on the internet for Boston Fudge Cake. Some are very modern and do not use sour milk, some use sour cream, some use buttermilk. From what I can tell, a fudge cake is going to be more like a brownie, more dense than a standard chocolate cake, and some have a pudding center. Some are served with icing, some as a layer cake, and some without icing, but with a chocolate or caramel pecan sauce topping. They all sound wonderful!
Boston Fudge Cake
2 cups brown sugar
1/2 cup shortening
Cream thoroughly. Add yolks of 2 eggs. Beat well. Then add 2 squares of bitter chocolate (melted) 1/2 up of water. Dissolve 1 teas. soda in the water. 1/2 cup sour milk. 2 cups sifted flour. Last of all fold in the beaten egg whites. Bake in a slow oven.