For: shirred eggs, calf’s brains, boiled or sautéed fish, chicken breasts, vegetables
A properly made brown butter sauce has a deliciously nutty smell and taste, but is never black despite the poesy of the title. When you heat butter to the boil, its milk solids begin to darken from golden nutty, noisette, to golden brown, noir, but you never let it darken to black, burned, and bitter. It is a quick sauce, and you can make it right in the pan when you are serving it over browned foods like liver or sautéed chicken breasts. For pale foods like poached eggs or poached calf’s brains, make it separately and pour the browned butter off the dark sediment in the pan.
Making the sauce in the sauté pan—just before serving
Cut the butter into pieces, and add to pan after food has been sautéed and removed. Salt and pepper food if necessary, and sprinkle the parsley over it. Holding sauté pan by handle, swirl over moderate heat as butter foams up; it will begin to color as foam subsides. At the moment the butter is a nutty brown—a matter of seconds—pour it over the food. Then add the vinegar, lemon juice or capers to the pan, rapidly boil down to reduce excess acidity, pour over the brown butter, and serve at once.
Making the sauce separately—may be done in advance
Cut the butter into pieces and add to a small saucepan. Swirl pan by its handle over moderate heat as butter melts and foams up. Continue cooking for a few seconds as foam subsides and butter starts to color. As soon as it is a nutty brown, remove from heat and let sediment settle for a moment. Either pour clear brown butter over hot food that you have seasoned and sprinkled with parsley, or pour the butter off its sediment and into a bowl or another pan. Rinse out butter pan, add vinegar, lemon juice or capers, and boil down rapidly to reduce excess acidity. Either pour over the food and serve; or pour the browned butter back in, set aside, and reheat before serving.