Make the Det Mix: Combine all the ingredients in a bowl.
Make the hamburgers: Heat the butter and oil in a large cast iron skillet over high heat. Add the hamburgers and cook halfway through and turn over. Cover each with about 1/4 cup of the Det Mix and top with the onion slices. Pour in the 1/4 cup beer and cover with a lid. Steam a couple of minutes until the onion is translucent. Re-steam with beer a couple of times. Top each hamburger with a slice of cheese and cover until melted. Transfer the hamburger to the buns and serve.
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. Form into patties¿a 6 to 8-ounce patty for an average serving.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.
Recipe adapted from the Del Rio Bar, Ann Arbor, Michigan