1. 1. Roast the Butternut Squash: Preheat your oven to 400 F (200 C). On a large baking sheet, toss the cubed butternut squash with 2 tablespoons of olive oil, 1/2 teaspoon of salt, and 1/4 teaspoon of black pepper. Spread the squash in a single layer. Roast for 20-25 minutes, or until the squash is tender and slightly caramelized. Once roasted, transfer the squash to a food processor or blender and puree until completely smooth. Set aside. You want it to be a silky, uniform consistency, almost like baby food.

2. 2. Cook the Pasta: While the squash is roasting, bring a large pot of salted water to a rolling boil. Add the elbow macaroni and cook according to package directions until al dente. This usually takes about 7-9 minutes. Drain the pasta well and set it aside. Do not rinse the pasta, as the starch helps the sauce adhere better.

3. 3. Prepare the Roux: In a large saucepan or Dutch oven, melt the 4 tablespoons of unsalted butter over medium heat. Once the butter is melted and slightly foamy, sprinkle in the 1/4 cup of all-purpose flour. Whisk continuously for 1-2 minutes until a smooth paste, or roux, forms. It should smell slightly nutty and be a pale golden color. This is the base that will thicken your cheese sauce.

4. 4. Whisk in the Milk and Seasonings: Gradually whisk in the 3 cups of milk, a little at a time, ensuring there are no lumps. Continue whisking until the sauce is smooth and starts to thicken, about 5-7 minutes. It should be thick enough to coat the back of a spoon. Stir in the remaining 1/2 teaspoon of salt, 1/4 teaspoon of black pepper, 1/2 teaspoon of garlic powder, and 1/4 teaspoon of ground nutmeg.

5. 5. Add the Cheese and Butternut Squash Puree: Reduce the heat to low. Add the shredded sharp cheddar cheese and Gruyere cheese to the sauce, stirring constantly until the cheeses are completely melted and the sauce is smooth and creamy. Once the cheese is fully incorporated, stir in the smooth butternut squash puree. Mix well until the sauce is uniformly orange and creamy. Taste and adjust seasonings if needed.

6. 6. Combine with Pasta: Add the drained cooked macaroni to the cheese sauce. Stir gently until all the pasta is evenly coated with the rich, creamy butternut squash cheese sauce.

7. 7. Serve: Transfer the mac and cheese to serving bowls. If desired, sprinkle with grated Parmesan cheese and fresh chopped parsley for garnish. Serve hot and enjoy! The cheese will be bubbling and the pasta will be perfectly coated.