10. Place the butter(1/4 cup) in a medium pot (with a lid){} over medium heat. Let melt, then add the olive oil(2 tbsp) and walnuts(1 cup). Cook until the walnuts are lightly toasted and the butter is golden brown, 2 to 3 minutes.
11. Use a slotted spoon to transfer the walnuts to a paper towel lined plate. Add the garlic(3 cloves) and sage(1 tbsp) to the pot and cook briefly until golden and aromatic, about 1 minute.
12. Add the butternut squash(6 cups), chicken broth(2 cups), salt(1 tsp) and pepper(1/2 tsp). Bring to a simmer, then cover and cook for 15 to 20 minutes, or until the squash is fork tender.
13. Transfer the squash mixture to a blender. Cover, then remove the top insert from the lid and cover with a kitchen towel (to let steam escape). Puree until very smooth, about 1 minute.
14. Meanwhile, bring a large pot of water to a boil. Season with salt. Add the penne pasta(1 lb) and reduce to medium heat (just simmering). Cook 1 minute less than the package directions. Reserve 1/2 cup of the pasta water(1/2 cup) then drain the pasta in a colander.
15. Return the large pot to medium heat. Add the butternut squash sauce, heavy cream(1/4 cup), cooked pasta and 1/4 cup of the pasta water and parmesan cheese(1/2 cup). Stir gently with a rubber spatula, until the sauce has thickened slightly and is coating the pasta, about 2 minutes. (Add more pasta water to reach desired consistency). Season with more salt and pepper to taste.
16. Serve immediately topped with more chopped sage, parmesan cheese, and the reserved walnuts.