from Not Your Mother's Slow Cooker Recipes for Entertaining by Beth Hensperger
Slow cooker capacity: 3-4.5 quarts
Setting and cook time: Low for 9-11 hours
1 medium-size to large sweet potato
6 medium-size carrots
1 medium-size to large sweet onion, such as Walla Walla or Maui (we used a yellow onion)
One 1-inch-long piece of fresh ginger
4 cups chicken or vegetable broth
Salt and white pepper to taste (we used black pepper)
Yogurt, creme fraiche, or heavy cream for garnish (we used plain Greek-style yogurt)
1. Peel the sweet potato and chop into pieces no larger than 1 inch on a side. Peel the carrots and chop into pieces no larger than 3/4 inch on a side. Peel the onion and chop into 3/4-inch pieces. Use a vegetable peeler or a paring knife to peel the ginger. Mince it finely. Place the sweet potato, carrots, onion, and ginger in the slow cooker and stir to combine. (This is where Geoff and I put the crock in the fridge until the next morning.) Add the broth. If you are using canned broth, do not add salt or pepper at this point. If you are using unseasoned homemade broth, add 1/2 teaspoon salt and a dash of white pepper. Cover and cook on LOW until the vegetables are quite tender, 9 to 11 hours.
2. Turn the slow cooker off, uncover, and allow the soup to cool for a few minutes, then puree in a blender or food processor, in batches if necessary, or use an immersion blender right in the crock. You will want to obtain the smoothest puree possible, so let the blender do its work for a few minutes. Check the seasonings and add salt and pepper if necessary. Serve the soup hot or cold, garnished with a spoonful of yogurt, if desired.