In a small bowl whisk together sour cream, 1/2 and 1/2 and cornstarch, whisk well so that there are no clumps. Put mixture in a food processor and add fresh basil. When the veggies are done, gently scoop entire contents into food processor and pulsate until everything is combined and sauce doesn't have any big vegetable chunks, there will be little veggie flecks...so good!