Easy Cheesy Hot Beef Sandwiches with Gravy (30-Minute Dinner)

Ingredients

• 2 tablespoons unsalted butter
• 1 small yellow onion, finely chopped
• 2 garlic cloves, minced
• 2 tablespoons all-purpose flour
• 1 1/4 cups (300 ml) beef broth
• 1/2 cup (120 ml) whole milk
• 1 teaspoon Worcestershire sauce
• 1/2 teaspoon kosher salt, plus more to taste
• 1/4 teaspoon black pepper
• 1 lb (450 g) thin sliced roast beef
• 4 sturdy sandwich rolls or hoagie rolls, split
• 2 tablespoons softened butter, for rolls
• 4 slices provolone cheese
• Pickles or pepperoncini, for serving, optional