Season Steak: Pat dry and season both sides with salt, pepper, paprika, and garlic powder.
Sear Steak: Heat oil in a skillet, sear steak for 2-3 minutes per side, then set aside.
Cook Vegetables: Sauté onions and garlic in the same skillet until soft.
Assemble in Crockpot: Add steak, sautéed veggies, broth, Worcestershire sauce, and optional mushrooms to the crockpot.
Slow Cook: Cover and cook on low for 6-8 hours or high for 3-4 hours.
Thicken Sauce (Optional): Mix 2 tbsp flour with 1/4 cup cooking liquid, stir back into the crockpot, and cook for 15-20 minutes.
Serve: Plate steak, pour sauce over the top, garnish with parsley, and serve with your favorite sides.