Instructions

• Combine egg and mustard in the bowl of a food processor fitted with a blade attachment; mix until evenly combined.
• With the processor running, slowly add the oil in a thin stream until it is completely combined. Turn off the processor, then add the vinegar or lemon juice and pulse until the mixture is smooth.
• Season to taste with salt and pepper (and any additional add-ins you like) and store in an airtight container, such as a mason jar with a rubber seal, in the fridge for up to four days.