Ingredient:

• 1 pound uncooked elbow macaroni
• 4 tablespoons butter
• 1/4 cup all-purpose flour
• 2 cups 2% milk
• 1-1/2 cups shredded cheddar cheese
• 1 cup shredded Gruyere cheese
• 1-1/4 teaspoons salt
• 1/2 teaspoon pepper
• 1/4 teaspoon garlic powder
• 1/4 teaspoon ground mustard
• 1/8 teaspoon ground nutmeg
• 1 tablespoon truffle oil, divided
• 1/2 cup panko bread crumbs
• 1/4 cup grated Parmesan cheese
• 2 tablespoons minced chives, optional