Butternut Squash and Sweet Potato Soup

Melt the butter in a large stock pot over medium heat. Stir in the onion; cook and stir until the onion has softened and turned translucent, about 5 minutes. Add the butternut squash, sweet potatoes, and enough vegetable broth to cover. Stir in the thyme, ginger, turmeric, coriander, black pepper, and chile pepper. Bring to a boil over medium-high heat, then reduce heat to medium-low. Cover and simmer until vegetables are very tender, 20 to 30 minutes, stirring occasionally. Remove and discard the chile pepper. Pour about 1/3 of the soup and 1/3 of the tofu into a blender, filling the pitcher no more than halfway full. Hold down the lid of the blender with a folded kitchen towel, and carefully start the blender, using a few quick pulses to get the soup moving before leaving it on to puree. Puree in batches until smooth and pour into a clean pot. Repeat with the remaining soup and tofu. Alternately, you can use a stick blender and puree the soup and tofu right in the cooking pot.