Heat oven to 350 degrees F. Grease and generously flour a deep 8-inch square cake tin, two 8-inch round pans, or a small tube pan.
Cream the butter, stir in sugar until it is well mixed, then add eggs. Dissolve soda in the milk. Sift together the presifted flour, cocoa, cinnamon, ginger, and salt; add to creamed mixture alternately with the milk and soda mixture. Add the vanilla and beat 100 times by hand (today I use my portable electric mixer).
Pour into the prepared pan or pans and tap pan on counter a few times to release any bubbles in the batter. Bake until cake begins to shrink from sides of pan and toothpick or broom straw comes out clean when inserted in center. I start testing about halfway through anticipated baking time, which will vary from about 25 minutes in 2 round pans to 45 minutes in a square pan and 50 to 55 minutes in a tube pan. Cool on wire rack for 5 to 10 minutes before removing from pan.
This is a versatile cake, delicious served warm with a dollop of whipped cream and perhaps a garnish of fresh berries in season, or simply sprinkled with a bit of sifted confectioners’ sugar.