Cream butter and sugar well. Stir in molasses and mix well. Stir soda into the sour milk. (To turn sweet milk sour quickly, and 1½ tablespoons of lemon juice or 1 1/3 tablespoons of vinegar to lukewarm sweet milk. Let stand a few minutes to sour before you use it.) Add milk alternately to the creamed mixture with the sifted dry ingredients and the eggs. Beat well after each addition of the beaten eggs.
Pour into 2 greased and floured baking pans (9 × 12). Bake 45 to 55 minutes in a preheated 325° oven.
Serve plain or warm with your favorite hard sauce.