Add the chopped onion to a large pot with a tablespoon or two of water and sauté over medium heat until softened, about 5 minutes. Then add the garlic, squash, and sweet potato and cook for another 2-3 minutes.
Next, add your broth, pumpkin puree and all your seasonings. Bring to a low boil, and cook for about 8-10 minutes until the veggies are fork tender.
Using an immersion blender, purée your soup until smooth and creamy. Serve garnished with parsley and pumpkin seeds if desired.
If you do not have an immersion blender, you may carefully transfer to a regular blender, processing small portions at a time. Use extreme caution and do not fill the blender to the top when blending hot liquids as this can cause spillage and burns.