Minced beef hamburgers with a beef stock pan sauce (Julia Child)

Chop the onions very finely. Over medium heat, melt the butter in a frying pan; when it foams add the onion and cook about 10 minutes until very tender but not browned.

In a mixing bowl combine the beef, the cooked onions, salt, pepper, thyme and the egg; mix by hand (the book says beat vigorously with a wooden spoon).

Work in the softened butter or pork fat.

Form into four patties three quarters of an inch thick; cover with wax paper and refrigerate until needed.

Heat butter and oil over medium heat to film the bottom of the frying pan. Roll each patty very lightly in flour and shake off the excess.

When the butter foams, add the patties and cook two to three minutes per side for medium well, basting, until a good crust forms on both sides.

Pour the fat out of the pan, return to the heat, add the beef stock and boil it down, scraping up the browned bits, until almost a syrup.

Off the heat, add room temperature butter a little at a time until it absorbs into the sauce. Pour over the patties.