In a food processor, fitted with a metal blade, combine the egg, garlic, mustard, lemon and lemon juice. Process until smooth. Season with salt and pepper.
With the machine running, slowly add the oil in a steady stream, until an emulsion forms. Season with salt and pepper. Place the mayonnaise in a mixing bowl. Fold in the chopped herbs.
Cover and refrigerate for 2 hours before serving.
Serve the mayonnaise as a dipping sauce for fried seafood or a spread for sandwiches.
Consumption of raw or undercooked eggs, shellfish and meat may increase the risk of foodborne illness.