1 small onion, peeled and sliced into thin half moons
1 lb. fettucine
1/4 c. heavy cream
1 TBS butter
1 small bunch sage
Preheat the oven to 375°F. Peel the butternut squash and cut into slices that are half an inch thick. Place on a baking sheet and drizzle with the olive oil, then sprinkle with salt and pepper. Flip slices with a spatula to coat with the oil. Roast until fork tender and slightly caramelized, about 20-25 minutes, checking and flipping after 10 minutes. When tender, remove from oven and place in a blender. Set aside.
Heat a medium frying pan over medium heat and add the pancetta cubes. Cook until crispy and browned on all sides, stirring frequently. Once cooked, set aside on a paper-towel lined plate. Discard all but 2 TBS of the pancetta grease. Heat the 2 TBS of grease over medium-low heat, then add the sliced onions to the pan. Cook, stirring frequently, until thoroughly caramelized and slightly crispy, about 15 minutes.
While the onions are cooking, bring a large pot of heavily salted water to a boil. Cook the fettucine according to package directions and drain, reserving 1 cup of the pasta water. Place the cup of pasta water in the blender with the squash and the 1/4 c. heavy cream, and puree until very smooth. Toss the squash puree with the fettucine.
Just before serving, melt the 1 TBS of butter in a small frying pan. Fry the sage leaves in the butter until crispy, about 2 minutes. To assemble, divide the pasta between the serving plates, and top generously with cooked pancetta, caramelized onions, and fried sage. Serve immediately.