Ingredients
1tspbutter
1cupred onion,finely chopped
3lbsground beef
1cupmushrooms,chopped
½cupketchup
4egg yolks
¼cupWorcestershire sauce
2tbsphorseradish mustard
4tspblack pepper,ground
1tbspsea salt
Preparation
Heat the butter in a skillet over medium heat, and cook and stir the red onion for about 5 minutes until soft and translucent.
Mix the ground beef, cooked onion, mushrooms, ketchup, egg yolks, Worcestershire sauce, horseradish mustard, black pepper, and sea salt in a large bowl until thoroughly combined.
Form the mixture into 6 ¾-inch thick patties and cook in a large skillet over medium heat for 5 to 7 minutes per side until the burgers are juicy and browned,
An instant-read meat thermometer inserted into the center of a patty should read at least 160 degrees F.
