1. Put about 4 cups cold water and the salt into a large saucepan. Add the sweet potato, butternut squash, and delicata squash. (You should have enough water to cover the vegetables.) Bring them to a boil and let them cook until you can put a knife through the sweet potato. Drain the squash and potato and set aside. While the sweet potato and squashes are cooking, heat 2 tablespoons of the olive oil in a skillet. Add the onions and garlic. Cook on medium to low heat until they are soft. Add the sage and rosemary. Cook for one more minute. Add the spices to the onions and herbs. Put the vegetables and the onion mixture into a food processor. Blend until smooth. Add the butter and remaining olive oil. Season to taste.