In a Vitamix or other strong blender, combine the aquafaba, cashews, garlic, lemon juice, Dijon and salt. Secure the lid and process, starting on a lower speed and increasing until the cashews are smoothly pureed. Stop and scrape down any bits of cashew that are on the sides of the blender container.
Cover the blender and blend for 4 minutes.
Take the plug from the lid and insert a funnel. Scrape down and replace the lid. Turn the blender on at low speed, and start drizzling the oil through the funnel, with the machine running. Go very slowly, it should take 3-4 minutes to slowly trickle it in.
When the mixture is thick and creamy, scrape into a jar and chill for at least an hour to thicken completely. Store for up to a week in the refrigerator, tightly covered.