Put the green onions, garlic, horseradish, mustards, ketchup, hot sauce, Worcestershire, lemon juice, egg, salt, and cayenne in a food processor or blender and process until smooth, about 30 seconds. With the motor running, slowly pour in the vegetable oil through the feed tube. The mixture will thicken.
Transfer to a container, cover, and refrigerate for 1 hour before using. Best if used within 24 hours.
Yield: about 2 cups
Salmonella warning: Let’s talk about egg safety because I don’t want any of you out there to get sick. I personally love homemade fresh mayonnaise and I make it with fresh—and I mean FRESH—raw eggs. I’ve never had any trouble, but I want you to take some precautions. Always purchase your eggs from a reputable source, a place you can trust with your life. Don’t use eggs after the expiration date on the carton. Don’t go leaving your eggs in the backseat of your car while you’re out and about, and once you get home, keep the eggs in the refrigerator. I use eggs pretty quickly, so I don’t have to worry about keeping them too long at home. But I suppose there’s a tiny risk some nasty old salmonella could sneak into some eggs, so just be cautious about serving young kids or the elderly or to people who have health problems. Okay?