1 butternut squash that will fit in your crock pot
2 Tbsp. water
1 large yellow onion
1 Tbsp. olive oil or vegetable oil or unsalted butter
4 c. chicken or vegetable broth
1 tsp. light brown sugar
Salt and freshly ground black pepper to taste
Sour cream, plain yogurt, or creme fraiche
Pinch of cumin seeds or pepitas, toasted in a dry skillet over medium heat until fragrant
Wash and dry the squash and place it in the slow cooker. Add the 2 tablespoons of water. Cover and cook on LOW until the squash is tender, 7 to 9 hours. When the squash is done, a wooden skewer or a paring knife will pierce it easily and slip through to the center. If the squash is not done, replace and cover and continue to cook on LOW, checking every 30 minutes. Allow the cooked squash to cool. Do not discard any liquid in the slow cooker.
While the squash is cooking, peel and chop the onion. In a medium-size non-stick skillet, heat the oil over medium heat. Add the onion and cook, stirring, until softened, about 5 minutes. Set aside.
Slice the squash in half lengthwise. Use a soup spoon to scrape out the stings. Discard them. Scoop out the cooked flesh and discard the shell. In a blender, puree half the squash with half the onion and about c cups of the broth. Pour the puree into the slow cooker and stir to dissolve any caramelized squash juices that have stuck to the bottom. Puree the remaining squash and onion with the remaining 2 cups of broth and add to the cooker. Add the brown sugar and season with salt and pepper. Cover and cook on HIGH until the soup is hot, about 1 hour.
Taste and correct the seasonings, if needed. Serve the soup hot. If desired, top with a dollop of sour cream, yogurt, or creme fraiche and a few toasted cumin seeds or pepitas.