Serve this delightful sauce over bread puddings, apple dumplings, coffee cake, baked apples, soufflés, puddings, blackberry cobbler.
Return the mixture to the saucepan. Over low heat, stir constantly with a wooden spoon until the mixture thickens. Be careful not to overcook or the eggs will scramble. The sauce is finished when you can dip a spoon into it, then draw your finger over the back of the spoon and have a track remain that is almost free of sauce.
Remove the sauce from the heat and stir in the vanilla. Serve, or chill in refrigerator (covered with plastic wrap) and use later.