From 1911:

Three eggs well beaten, whites and yolks separately. Cream one cup of sugar with yolks and one teaspoon of
vanilla, one tablespoon of milk, then one cup of sifted flour, to which add one teaspoon of baking powder. When all is beaten put in whites of eggs; bake in a buttered tin in a moderate oven. When cold divide four layers with a strong linen thread, wet each layer with strong black coffee, then fill with the following:
Filling — Half pound butter and a quarter of a pint of sugar; stir till smooth; beat one by one yolks of three eggs; then strong black coffee to taste.