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Trim away and discard the long piece of fat running down the side of the steaks.

Marcus Nilsson for The New York Times. Food Stylist: Brian Preston-Campbell. Prop Stylist: Angharad Bailey.

Ingredients

For the chipotle mayonnaise:

• ¾ cup mayonnaise
• 3 chipotle peppers in adobo sauce, minced, or more to taste

For the sandwiches:

• 2 tablespoons neutral cooking oil, like canola
• 1 large white onion, peeled and sliced thin
• 2 red bell peppers, seeded and sliced thin
• 1 green bell pepper, seeded and sliced thin
• Kosher salt and freshly ground black pepper to taste
• 1 tablespoon unsalted butter
• 1 pound button mushrooms, cleaned and sliced thin
• 2 ½ pounds skirt steak, cut into 6 equal-size sections
• 6 large sub rolls or Italian bread cut into 6 submarine-shaped pieces of 8 to 10 inches, sliced down the center
• ½ pound sharp Cheddar cheese, sliced thin

• Nutritional Information

Preparation

1. To make chipotle mayonnaise: Combine mayonnaise and minced peppers in a small bowl and stir well. (Leftover sauce may be covered and stored safely in the refrigerator for weeks.)
2. To make toppings for sandwich: Heat a griddle or a large, heavy frying pan, ideally cast iron, over medium heat. Add oil to pan and, when it begins to shimmer, add the onion and peppers and stir to combine. Cook, stirring every so often, until they begin to soften and brown, approximately 15 to 20 minutes. Season to taste with salt and pepper, remove and set aside. Wipe pan, add butter and repeat process with mushrooms. Cook until they have released their juices and are soft and glazed, about 6 minutes. Remove and set aside.
3. To make steaks: Heat griddle or frying pan over high heat until nearly smoking. Season meat aggressively with salt and pepper. Place steaks on griddle, working in batches if necessary, and cook for 3 minutes each side, until well browned but very rare. Remove to a serving platter and allow to rest.
4. To make sandwiches: Preheat oven to 200 degrees. When steaks are complete, slice them against the grain as thinly as possible. Place sub rolls in oven to warm. Return sliced steaks to griddle or frying pan, over medium heat, and add onions, peppers and mushrooms. Stir to combine, turn heat to low and cover with sliced cheese. Using tongs and a wide spatula, stir and pull to combine as cheese melts, approximately 3 minutes.
5. To serve: Remove rolls from oven and spread chipotle mayonnaise on the interior of each serving. Fill each sub with a mixture of meat, vegetables and cheese. Serve immediately.