1 tablespoon heavy cream
Freshly ground black pepper
Vegetable oil, as needed
Kosher salt, to taste
Spread the meat out on a board and grate 2 to 3 tablespoons of onion into it—use a fairly fine grater so you get just the juice and very finely grated raw onion. Now mix in about a tablespoon of heavy cream and some freshly ground black pepper, to taste. Form into patties--a 6 to 8-ounce patty for an average serving.
Using a black iron skillet or your best copper one or your pet aluminum frying pan, Teflon-coated or not (with a Teflon coating you won't need much fat, just a little bit for flavor), and cook the hamburgers in the butter and oil over fairly high heat, giving it 4 to 5 minutes a side, depending on how well done you like it. Salt this creamy, oniony, peppery hamburger before serving it on a buttered bun or English muffin, or as a main course with sliced tomatoes and onions or some home-fried potatoes.
We cooked ours on the grill using the two-zone fire method. Sear it hot so it gets a nice char/crust and then finish it over the cooler section of the grill until it's the way you like it.