Mac and Cheese - Once Upon a Chef

Ingredients

• 16 oz macaroni, cavatappi or penne pasta
• 1/2 cup (1 stick) unsalted butter, divided, plus more for greasing the pan
• ½ cup all-purpose flour
• 5 cups whole milk
• 12 oz Gruyere, (shredded (about 4 cups))
• 8 oz extra-sharp Cheddar, (shredded (about 2 cups))
• 2/3 cup grated Parmigiano-Reggiano
• 1 teaspoon salt, (plus more for the pasta water)
• ½ teaspoon freshly ground black pepper
• ¼ teaspoon ground nutmeg
• 1 cup panko breadcrumbs
• 1 teaspoon herbes de Provence or dried thyme