Slice Sirloin Steak (1 pound).
Add the steak pieces to a bowl. Pour over Olive Oil (2 tablespoon) and mix with your hands to coat the meat.
Season with Paprika (2 teaspoon), Dried Oregano (1 teaspoon), Kosher Salt (1/2 teaspoon), and Ground Black Pepper (1 teaspoon). Use your hands to massage the seasonings into the steak. Let rest for 15 minutes.
Heat Olive Oil (2 teaspoon) in a large skillet over a high heat. Add steak pieces and allow them to sit in the pan for a moment to sear. When the steak begins to sear, move it around and cook until it is no longer pink. Remove from the heat.
Heat additional olive oil. Add Onion (1) and cook on medium high for about 8 minutes.
Add White Mushroom (1 1/2 cup) and cook until light brown and tender, about 2 minutes.
Combine onion and mushroom mixture with the steak in a bowl.
Into a mixing bowl, add Salted Butter (6 tablespoon), Olive Oil (2 tablespoon), Dried Parsley (2 teaspoon), and Garlic Powder (2 teaspoon). Mix well.
Brush one side of each slice of White Bread (12 slice) with the garlic spread.
Heat a nonstick skillet over medium heat. Place two slices of bread into the pan, buttered side down. Place a layer of Mozzarella Cheese (to taste) over both slices of bread.
Add an even layer of the steak and onion mixture, then top with another layer of cheese. Place another slice of bread on top of each, buttered side up.
Cover both of the sandwiches with foil and, with a heavy object such as a pan, smash both of the sandwiches down as fast as you can. Work quickly so they won’t burn.
Once the bottom of the bread has browned, carefully flip the sandwich and cook the other side.