Yolks of three eggs, half a cup of sugar, beaten together, and half a cup of butter.
Melt all carefully over slow heat until it is clear like honey. Do not let boil. Before taking off the fire stir in a teaspoonful or more strong vanilla essence.
Another recipe for vanilla butter is:
Beat ¼ lb. butter to a cream with 2 tablespoonfuls of sugar, and vanilla to taste. This is really American “hard sauce” for serving with steamed puddings, or for using as a filling between sandwich cakes.