1 pound flank steak
1/2 cup red wine vinegar
1 lime, zested and juiced
1/4 cup chopped cilantro leaves
1 tablespoon hot sauce
1 teaspoon Worcestershire sauce
1 teaspoon salt
1/2 teaspoon fresh ground black pepper
2 tablespoons unsalted butter
3 tablespoons all-purpose flour
2 chipotle chiles in adobo (canned), chopped
1 tablespoon adobo sauce (from chipotle can)
1 1/2 cups heavy cream
1 cup processed grated Cheddar
1 tablespoon vegetable oil, plus more if needed for steak
1 red bell pepper, cut into strips
4 hoagie rolls
1 avocado, pitted and flesh sliced 1/4-inch thick
1 cup cilantro leaves
Place flank steak, red wine vinegar, zest lime juice, cilantro, hot sauce, Worcestershire, salt and ground black pepper in a large plastic bag. Marinate for 1 hour in the refrigerator. Remove flank steak and pat dry. Place in freezer for 1 hour.
Meanwhile, prepare the sauce: Melt butter over medium heat-high heat in a sauce pot. Add flour, chipotle and adobo sauce, stir to combine. Add heavy cream slowly, stirring well with each addition to incorporate. Add cheese and stir until melted. Keep over low heat while finishing sandwich.
Remove flank steak from freezer and slice on the bias against the grain into 1/4-inch thick pieces. Heat 1 tablespoon of oil in a cast iron griddle or skillet, and saute the red peppers until they blacken around the edges, and soften, about 8 minutes. Remove from griddle and turn heat to medium-high, add more oil if necessary and sear steak in batches, about 2 minutes.
To assemble the sandwiches: Cut bread loaves in half, leaving 1 side attached. Layer on avocado slices, top with flank steak, red pepper, and cilantro. Drizzle with chipotle cheese sauce and serve immediately.