Creamed Spinach Mac & Cheese

Name: Creamed Spinach Mac & Cheese
Prep time: 15 min
Cook time: 30 min
Total time: 45 min
Cuisine: American
Ingredients: 1 pound elbow macaroni; Salt, for pasta water; 3 tablespoons unsalted butter; 1 small onion, finely chopped; 2 cloves garlic, minced; 3 tablespoons all-purpose flour; 2 cups whole milk; 1 cup heavy cream; 1/2 teaspoon ground nutmeg; Freshly ground black pepper, to taste; 1 (10-ounce) package frozen chopped spinach, thawed and drained; 4 cups shredded sharp cheddar cheese; 1 cup grated Parmesan cheese; 1 teaspoon mustard powder (optional); 1/2 cup panko breadcrumbs (optional)