Combine the egg yolk, lemon juice, ginger, garlic, and green onions in a food processor and process for 15 seconds. With the motor running, slowly add the vegetable oil through the feed tube. The mixture will thicken. Add the soy sauce, cilantro, pepper, sesame oil, and salt. Pulse once or twice to blend. Serve immediately or store in an airtight container for no more than 24 hours before using.
Makes about 1 cup