Walnut Plum Pudding

From 1922:

Chop one cupful suet, mix with 1 cupful raisins, 1 cupful currants; 1 cupful chopped walnuts, sift together 1 cupful flour, 1 teaspoonful baking powder, 1 teaspoonful each of cinnamon, cloves, and nutmeg, add 4 eggs, 1 cupful brown sugar, and enough milk to make a stiff batter – about 1 ½ cupfuls will be needed. Flavor with 1 cupful vanilla, stir in ½ cupful molasses; steam 3 hours and serve with sauce.