Start by cutting 1 ¼ pounds sirloin steak into 1-inch cubes. Add 1 tablespoon olive oil to a medium-sized skillet over medium-high heat. Season steak with salt and pepper and add them to the pan cooking them until they are golden brown.
Remove the steak and set it aside on a plate. Add 8 ounces mushrooms and 3 cloves garlic to the pan and cook until tender. Add 1 cup heavy cream, ½ cup shredded parmesan cheese, 1 teaspoon Italian seasoning, ½ teaspoon salt and ¼ teaspoon pepper. Add the steak back to the pan and allow it to heat through and the sauce to thicken.
Serve over rice or pasta and garnish with chopped parsley.