Preheat oven to 425°F (220°C). Bring salted water in a large pasta pot to a boil. While the water is coming to the boil, heat olive oil in a skillet. Sauté onion and garlic with chili flakes, sage and salt and pepper to taste in olive oil until onions are translucent. Set aside.
Cook the pasta and squash in the same pot until tender. Measure out 1 1/4 cups (300 mL) pasta water, then drain the pasta and squash. Set the pasta and squash aside.
In the pasta and squash pot, mix the reserved pasta water, milk, goat cheese, onion-garlic mixture, toasted walnuts (reserve 2 tbsp (30 mL) aside for topping), bacon and 1/3 cup (75 mL) of shredded cheese. Add the squash and pasta and toss together until well mixed.
Transfer pasta mixture to a 9 x 9-in (2 L) baking dish. Top with the reserved walnuts and remaining cheese. Season with pepper. Bake for 20 minutes, or until top is golden brown. Let rest for 10 minutes before serving.
Option: For decoration and added flavour, toss 4 to 5 whole small sage leaves with a 1 tsp olive oil. Distribute on top of pasta before baking.
To make the bake vegetarian, omit the bacon
This recipe is an excellent source of vitamin A and an excellent source of calcium, iron and fiber.