Hamburger Steak with Onion & Mushroom Gravy

With the weather quickly changing from spring to summer I knew I had to take advantage of a cool day to make this Hamburger Steak with Onion & Mushroom Gravy.

This one was right up SP's alley with the mushrooms and mashed potatoes but my stomach is definitely in light summer mode and it seemed too heavy. It was delicious, so I'll definitely make it again in the fall or winter.

Hamburger Steak with Onion & Mushroom Gravy
As seen on Our Best Bites, adapted from Cooking Light

1 pound ground sirloin
kosher salt and freshly ground pepper
1 teaspoon butter
1 large white onion, vertically sliced (about 1 1/2 cups)
1 cup sliced baby portobello mushrooms
4-5 cloves garlic, minced
1 tablespoon all-purpose flour
1 1/2 cups low-sodium beef stock
1 teaspoon red wine vinegar

Divide the meat into 4 1/2?-thick patties. Season both sides with salt and pepper. Set aside.

Heat a large non-stick skillet over medium heat. When the pan is hot, add the patties and cook for 4-5 minutes and then flip and cook for another 4-5 minutes or until cooked through. Remove the patties from the pan and set aside. Drain off any excess fat/grease.

Heat the teaspoon of butter in the skillet. When melted, add the onions and sprinkle lightly with salt and freshly ground pepper. Cook, stirring frequently, until they become tender and start to caramelize, about 5-7 minutes (you may need to add an additional teaspoon of oil if the onions are burning or sticking). Add the mushrooms and garlic and cook until the mushrooms are tender, being careful not to let the garlic burn.

When the onions and mushrooms are cooked, sprinkle them with 1 tablespoon of flour and stir quickly to combine. Add the broth and vinegar and cook until thickened. Add the beef patties and heat through. Serve each patty over mashed potatoes and top with mushrooms, onions, and gravy.