Heat olive oil in a medium saucepan. Saute onions and garlic for 3-4 minutes until translucent. Add chipotles, coriander, cumin, allspice, and sugar substitute to the pan and cook for another 2 minutes. Add the pumpkin puree and chicken broth to the pot and simmer for about 5 minutes.
Using an immersion blender, blend the soup in the pot until smooth (if you don’t have one, add the soup to a traditional blender, blend and return to the pot when smooth). Add the heavy cream and red wine vinegar and simmer for another five minutes or so.
Taste, then season with salt and pepper as desired. Serve hot, garnished with sour cream (other optional garnishes shown: pepitas and cilantro).