124. Salsa Bianca

• 100 grams (about 3-⅓ ounces) of butter
• 1 tablespoon of flour

First put the flour on the fire with half the butter, and when it has turned nut brown, add the broth or water slowly, stirring constantly. Without letting it boil too hard, add the rest of the butter and the vinegar. Remove from the burner, fold in the egg yolk and send to the table. It should have the consistency of cream sauce made without flour. For an ordinary bunch of asparagus, 70 grams