French Onion Mac Cheese Oh Là Là Comfort

Ingredients

• 3 large yellow onions, thinly sliced (about 900g)
• 3 tablespoons unsalted butter (45 ml)
• 1 tablespoon olive oil (15 ml)
• 1 teaspoon granulated sugar (5 ml)
• 1/2 teaspoon kosher salt (2.5 ml)
• 1/4 teaspoon freshly ground black pepper (1.25 ml)
• 6 tablespoons unsalted butter (90 ml)
• 1/4 cup all-purpose flour (30g)
• 3 cups whole milk (720 ml)
• 1 cup beef broth (240 ml)
• 1/4 teaspoon ground nutmeg (1.25 ml)
• 1/2 teaspoon kosher salt (2.5 ml), or to taste
• 1/4 teaspoon freshly ground black pepper (1.25 ml), or to taste
• 8 ounces Gruyère cheese, shredded (about 225g)
• 4 ounces sharp cheddar cheese, shredded (about 115g)
• 1 pound elbow macaroni (450g)
• 1/2 cup panko breadcrumbs (30g)
• 2 tablespoons melted unsalted butter (30 ml)
• 2 tablespoons chopped fresh parsley (optional garnish)