Philly Cheesesteak

INGREDIENTS

• 1 (12-ounce) flank steak, trimmed
• 1/4 teaspoon kosher salt
• 1/4 teaspoon freshly ground black pepper
• 2 (5-inch) portobello mushroom caps
• 2 teaspoons extra-virgin olive oil, divided
• 1 cup thinly sliced onion
• 1 1/2 cups thinly sliced green bell pepper
• 2 teaspoons minced garlic
• 1/2 teaspoon Worcestershire sauce
• 1/2 teaspoon lower-sodium soy sauce
• 2 teaspoons all-purpose flour
• 1/2 cup 1% low-fat milk
• 1 ounce provolone cheese, torn into small pieces
• 2 tablespoons grated Parmigiano-Reggiano cheese
• 1/4 teaspoon dry mustard
• 4 (3-ounce) hoagie rolls, toasted