Preheat your oven to 400°F (200°C). Toss the butternut squash chunks with olive oil, salt, and pepper, then spread evenly on a baking sheet. Roast for about 25-30 minutes until the squash is tender and caramelized around the edges.
While the squash is roasting, cook the pasta in a large pot of boiling salted water until al dente, according to package instructions. Drain and set aside.
In a saucepan over medium heat, warm the milk and add the minced garlic, cooking just until fragrant, about 1 minute. Remove from heat.
Once the roasted squash is cool enough to handle, transfer it to a blender or use an immersion blender to puree until smooth and creamy, adding a splash of the warm milk mixture to help blending if needed.
Pour the squash puree into the saucepan with the warmed milk and garlic. Stir in the grated cheddar cheese over low heat, stirring slowly until the cheese melts into a smooth, velvety sauce. Season with salt and pepper to taste.
Add the cooked pasta to the cheese and squash sauce, folding gently to coat every piece evenly in the rich, creamy mixture.
While the sauce is simmering, place the sage leaves in a small frying pan with a little olive oil over medium heat. Cook until crispy and golden, about 1 minute, then remove from heat.
Transfer the mac and cheese to a serving dish or spread in a baking dish. Top with the freshly fried sage leaves for a fragrant, crunchy garnish.
Optional: place under the broiler for 1-2 minutes to add a slight toasted finish on top, watching carefully not to burn the sage.
Serve hot, enjoying the creamy, velvety squash sauce with the crispy sage topping and perfectly cooked pasta.
