Heat a large nonstick skillet over medium-low heat. Add two teaspoons olive oil. Add onion and thyme and cook for around 17 minutes or until golden and tender. Increase the heat to medium-high and add vinegar, Worcestershire sauce and salt. Cook for 5 minutes or until almost all of the liquid is evaporated, stirring occasionally. Now remove the onion mixture from the pan and set aside. With the heat still at medium-high, add remaining 3 tablespoons of oil. Now add mushrooms and some salt. Sauté for about 8 minutes or until the mushrooms turn golden brown. Preheat grill or another skillet to medium-high heat. Get the cooked onion mixture from earlier and chop up 1 cup of it. Place beef into a large mixing bowl and stir the onion mixture along with salt and pepper into the beef. Now divide the beef mixture into 6 portions and form into patties. Gently press down in the center of each patty with your thumb. Grill patties for 4 minutes each side or until cooked to your liking. Top your burgers with arugula, mushrooms, onion mixture and whatever else you like!
*All of these ingredients can be found at our store!
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