In a large Dutch oven or heavy bottom pan heat the oil over medium high heat. Once the oil is hot, add the cumin, serrano peppers, and white parts of the scallions. Let this splutter for a few seconds and add the diced onion.
Cook the onions for about 15 minutes on medium heat, stirring occasionally, until the onions are golden brown. Use your spatula to scrape up any of the browned bits as you mix.
Next, lower the heat and add the tomato paste, taco seasoning, oregano, coriander powder, garlic, and stir for a few minutes until the garlic is fragrant but not browned.
Next add the canned tomatoes, cilantro, green chilis, chipotle sauce, pinto beans, and 3 cups of the vegetable broth. Stir well, put a lid on the pot, and cook on low heat for 20 minutes.
After 20 minutes, take 1.5 cups of the soup and place it in a blender. Carefully, blend the soup until smooth and add it back into the pot. This will help thicken the soup and give it a creamier consistency.
Add the remaining green parts of the scallions to the soup, and 1 cup of vegetable broth to the pot bring to a slow simmer and stir well. Taste for salt and serve hot with optional garnishes!