Blend the flour and butter in the saucepan without browning in the least. Add by degrees the boiling water or Consomme Blanc of Veal or Chicken, stirring until smooth, and boiling three minutes. Salt and pepper to taste. Add the juice of half a lemon. If the Sauce is to have other ingredients, this is the foundation for them. It must be of the consistency of thick starch to begin with, in the latter case.