Heat cast iron skillet over medium-high heat for 2 minutes. Add 1 tablespoon olive oil and swirl to coat the bottom. The pan should shimmer but not smoke, around 375°F.
1 tbsp olive oil
Add 1 lb ground beef in an even layer and let it sear undisturbed for 4-5 minutes. Break into large chunks with a wooden spoon after the bottom browns. Season with ½ teaspoon salt and ¼ teaspoon black pepper, then cook another 2-3 minutes until beef reaches 160°F and no pink remains.
1 lb ground beef, 0.5 tsp salt, 0.25 tsp black pepper
Push beef to edges of pan and add 2 tablespoon butter to the center. Once melted, add diced onion and cook 3 minutes until softened. Stir in minced garlic and 1 teaspoon dried thyme, cooking 30 seconds until fragrant.
2 tbsp butter, 1 medium onion, 3 cloves garlic, 1 tsp dried thyme
Add 8 oz sliced mushrooms spreading in a single layer. Let them cook undisturbed for 2 minutes to brown on one side, then stir and cook another 3-4 minutes until golden and tender. Increase heat if liquid pools to evaporate moisture.
8 oz mushrooms
Pour in ¼ cup beef broth and scrape bottom of the pan with a wooden spoon to release browned bits. Simmer 2-3 minutes until liquid reduces by half and coats beef and mushrooms. Taste and adjust salt and pepper before serving.
0.25 cup beef broth, 0.5 tsp salt, 0.25 tsp black pepper
