Place steak cubes in a mixing bowl; season with salt, pepper, paprika, garlic powder, and Italian Seasoning. Toss to combine.
Heat 1 tablespoon vegetable oil in a large cast iron skillet or a heavy-bottomed skillet over medium-high heat. Add the steak bites to the hot skillet in a single layer. If it doesn't sizzle, the skillet is not hot enough.
Sear the steak bites for 1 minute - do not move them around. Using tongs or a spatula, flip the steak bites over; add 2 tablespoons butter and stir in half of the minced garlic. Continue to cook for 1 to 2 more minutes or until the steak is done. Do not overcook the steak.
Transfer the steak bites to a plate and keep them covered.
Add remaining vegetable oil to the skillet and heat over medium-high heat. Stir in the sliced mushrooms and season with salt and pepper. Cook for 3 minutes, or until browned.
Add remaining butter and stir in the rest of the garlic; let cook for 2 to 3 more minutes or until soft. Stir the steak and drippings back into the skillet and cook for 30 more seconds or until heated through.
Remove from heat and let stand for 5 minutes.
Garnish with parsley and serve.