Scrumptious Steak Sammy

Directions

1. 1
   Season steaks with salt and pepper; allow steaks to come to room temperature, about 15 minutes.
2. 2
   Heat oil in a skillet over medium heat until very hot; lay steaks in pan and cook until they are beginning to firm and are hot and slightly pink in the center, about 5 minutes per side. An instant-read thermometer inserted into the center should read 140 degrees F (60 degrees C). Transfer steaks to a warm plate; cover and let rest, about 10 minutes.
3. 3
   Melt butter in same pan over medium heat; stir in mushrooms and peppers. Season with salt and pepper; cook and stir until tender, about 5 minutes.
4. 4
   Set oven rack about 6 inches from the heat source and preheat the oven's broiler.
5. 5
   Toast buns under the broiler until golden, about 2 minutes. Divide mozzarella cheese over bottom halves of buns; return to broiler until cheese melts, about 2 minutes.
6. 6
   Slice steak very thinly. Pile steak slices over cheese-topped bun halves; top with mushrooms and peppers. Spread mayonnaise on top halves of buns; place over sandwich.