Put a piece of butter the size of a pigeon's egg into a saucepan, and when it bubbles stir in with an egg whisk, an even tablespoonful of flour; let it continue to bubble until the flour is thoroughly cooked, when stir in half a pint of boiling water, or better still, of veal stock. When it boils take it from the fire, and stir into it gradually the beaten yolks of four eggs. Return the sauce to the fire for a minute to set the eggs without allowing it to boil. Again remove the sauce, stir in the juice of half a small lemon and fresh butter the size of a walnut, cut small to facilitate its melting. Stir all well with a whisk.