In bowl of food processor fitted with S-curve steel blade attachment, pulse together black beans, cocoa powder, maple syrup, grapeseed oil, water, vanilla extract, and salt until coarsely combined. Scrape down sides of food processor bowl with rubber spatula. Continue to blend until everything is thoroughly combined and smooth, pausing as needed to scrape down sides of bowl, about 2 to 3 minutes. Adjust consistency of dip to your liking by adding water a tablespoon at a time.