In a soup pot or dutch oven, heat 2 tablespoons of the oil on medium-high, and saute the onion, garlic, and squash, stirring frequently, until the onions soften, 10-12 minutes.
Add the broth, thyme, and nutritional yeast. Bring to a boil, then reduce the heat and simmer, uncovered, until the squash is tender, about 10 minutes.
While the squash simmers, heat the remaining 2 tablespoons of the oil in a frying pan on medium high. Add the collards and cook, stirring, until the collards become bright green and tender. Remove them from the heat and set aside.
Once the squash is tender, turn off the heat and grab your immersion blender (or do this in batches in a standard blender -- see notes), and puree the soup.
Once the soup is pureed, warm it up on medium, just until everything is heated through again, and season with salt and pepper. Serve topped with the collards.
Notes
DO NOT puree hot soup in a standard blender, because hot liquid in a blender can cause your blender top to fly into the air, splattering hot soup everywhere. Let the soup cool before blending, if you're not using an immersion blender.The prep time assumes that you are using pre-cut squash and collards and a garlic press. You can 100% prep these things by hand, if you prefer, but it will up the total time.I do not recommend using frozen butternut squash for this recipe. It tends to be too watery, and it doesn't get that richness that you get from fresh squash.