Heat oil in a large pot over medium heat.
Add the lemongrass, ginger, and turmeric powder to the pot. Stir for a few minutes until fragrant.
Add the butternut squash or pumpkin, along with 3 cups of water.
Bring the water to a boil and then reduce the heat to a simmer. Cook for 15-20 minutes or until the pumpkin or butternut squash is soft and easily pierced with a fork.
Remove the pot from the heat and allow it to cool slightly.
Transfer the contents of the pot to a blender and add the silken tofu or coconut milk.
Blend the mixture until smooth and creamy. If needed, add more water or vegetable broth to reach your desired consistency.
Taste the soup and adjust the seasoning if necessary. You can add salt, pepper, or other spices to enhance the flavor.
If needed, pour the soup back into the pot and heat gently until warmed through. I use a vitamix blender, which blends the soup hot so this step is not needed for me.