Cheesy Barley Gratin Recipe | Food Network UK

Ingredients

• 8 tablespoons (1 stick) unsalted butter, plus more for greasing the baking dish
• Salt and freshly ground black pepper
• 2 cups pearl barley
• 6 ounces Gruyere, shredded (about 2 cups)
• 2 cups shredded mozzarella
• 1 cup grated Parmesan
• 1 1/2 cups panko breadcrumbs
• 1 large onion, chopped into 1/4-inch pieces (about 2 cups)
• 2 large cloves garlic, finely minced
• 1 1/2 teaspoons finely-chopped fresh thyme
• 1/4 cup plain flour
• 4 cups whole milk