Freeze the steak for 30 minutes, then slice it as thinly as possible against the grain. Heat the oven to 350°F and grease a 9x13-inch baking dish.

Slice the bell pepper and onion into thin strips, slice the mushrooms, and mince the garlic.

Heat the avocado oil in a large skillet over high heat. Sear the steak in two or three batches, 1 to 2 minutes per batch, seasoning with half the salt and pepper. Transfer to the baking dish.

Lower the heat to medium, add the butter, and cook the pepper, onion, and mushrooms until soft and lightly browned, 6 to 8 minutes. Stir in the garlic for 1 minute, then spread the vegetables over the steak.

Whisk the eggs, softened cream cheese, heavy cream, and the remaining salt and pepper until smooth. Pour evenly over the steak and vegetables.

Lay the provolone slices over the top to cover. Bake 25 to 30 minutes, until the center is set and the cheese is bubbling and golden. Rest 10 minutes, then cut into 6 squares.