Heat oil in a dutch oven or soup pot over medium heat. Add onions and pinch of salt.
After about 10 minutes or once the onions turn soft and translucent, add garlic, ginger and serrano pepper.
After a couple minutes add the spices and let them bloom.
Add the stock, carrots, butternut squash. Cover and cook for 30 minutes, or until the vegetables are soft.
Puree with an immersion blender or in batches in a food processor or blender.
Garnish with raisins and serve.