01 - Preheat the oven to 400°F. Line a baking sheet with parchment paper.
02 - Toss the cubed butternut squash with olive oil, salt, and pepper. Spread evenly on the baking sheet and roast for 20 to 25 minutes until tender and caramelized.
03 - While the squash roasts, cook the pasta according to package instructions until al dente. Drain and set aside.
04 - In a large saucepan, melt butter over medium heat. Add chopped onion and cook for 4 to 5 minutes until softened. Add minced garlic and cook for 1 additional minute.
05 - Add roasted butternut squash, whole milk, salt, pepper, nutmeg, and paprika to the saucepan. Simmer for 5 minutes.
06 - Use an immersion blender or transfer the mixture to a blender and purée until smooth and creamy. Return to the saucepan if necessary.
07 - Stir in sharp cheddar and Parmesan cheeses until fully melted and the sauce is smooth. Adjust seasoning to taste.
08 - Add the cooked pasta to the cheese sauce and toss to coat evenly.
09 - For a baked topping, preheat the broiler. Combine panko breadcrumbs with melted butter and sprinkle over the pasta in an ovenproof dish. Broil for 2 to 3 minutes until golden brown.
10 - Serve immediately while hot.