1. Cut the butternut squash into cubes (Leave the skin on, it is edible) and steam them for 15 minutes.
2. Blend them with the goat cheese, olive oil, and water until you obtain a smooth sauce. Adjust the seasoning.
3. Meanwhile, lightly toast the pine nuts in a dry pan over low heat.
4. Cook the spaghetti according to the instructions on the packaging.
5. Put the cooked spaghetti back into the pot, off the heat. Add the sauce and arugula. Mix well.
6. Serve immediately, garnished with pine nuts, grated Parmesan, and basil.