In a heavy dutch oven or stock pot, heat oil over medium heat.
Add onion and cook until translucent but not browned.
Add garlic, chili powder, cumin, cocoa powder, chipotle in adobo, red pepper flakes and salt and pepper. Stir and cook about 1 minute, until well combined and fragrant. Add stock or water and butternut squash.
Bring to a simmer and cook over medium low heat until squash is very tender - approximately 25-30 minutes. Puree with immersion blender until completely smooth. If soup seems too thick, add more stock or water to desired consistency
Add black beans and greens and cook another 15-20 minutes or so until all ingredients are well blended, greens are wilted and beans are hot. Adjust seasonings.
Serve with avocado, cilantro and tortilla chips.