In a large stockpot, heat up 3 tbsp. of olive oil over medium high heat and sauté onion, carrots, and celery until they're soft and tender, about 10 minutes. You want them to be really soft and tender so the immersion blender will be able to blend it easily.
1 large onion, 2 carrots, 2 stalks of celery
When vegetables are soft, add in the chopped sage and stir around. Add in the chicken stock and the butternut squash puree.