Cream the butter, stir in the sugar gradually, add the unbeaten eggs, and beat all together until very creamy. Sift together one half cup of the flour, the cocoa and baking powder; use this flour first, then alternate the milk and remaining flour, using enough to make mixture stiff enough to drop from the spoon.
Add vanilla and beat until very smooth; then bake in loaf in moderately hot oven 35 or 40 minutes. Tests for baking cake.
It is baked enough when : It shrinks from the pan, touching it on the top, springs back, no singing sound.