Mock Mayonnaise

One cup vinegar, 1/2 teaspoonful mustard, a pinch of salt and of cayenne pepper, 1 teaspoonful flour, yolks of 2 eggs, 1 tablespoonful butter. Beat eggs and melted butter together. Put the vinegar on to boil, saving out a little to moisten the flour; salt, and pepper while cold. When the vinegar boils, add the thickening, stir till smooth, and then pour it into the eggs and butter. Set in ice box till ready to serve, and add 2 tablespoonfuls of olive oil, or cream to taste.