Sweet and Spicy Pumpkin Soup (vegan)

Cook 1 large onion, thinly sliced, in a little oil until soft and very brown. Add 1 large can pumpkin puree (not pie mix!), same volume stock or water, 2 T. vinegar, 1 t. chili flakes, and salt to taste. Cook on medium heat for about 10 minutes. Remove from heat and stir in 1/2 c. or more of coconut milk (optional). Serve.