Mayonnaise Dressing

From 1913:

During warm weather, when cream turns sour quickly, this is a good way to put it to use. The following mayonnaise dressing will keep in the icebox until used. It is simple and quickly prepared in a double boiler:

One cup vinegar, one cup sour cream, three eggs, one teaspoon ground mustard, two teaspoons sugar, salt, pepper, and paprika to taste. Mix all ingredients together and boil, stirring constantly until smooth. Just before removing from the fire add a lump of butter the size of a walnut.