Using a food processor add egg and yolk, mustard, salt and pepper. Mix on high for 30 seconds and pale yellow in colour.

With the food processor running, slowly drizzle in the oil until the mixture is emulsified and thick. Adding the oil slowly makes for a creamier mayonnaise. The total pouring time to aim for should be 1-1/2 to 2 minutes. With the food processor still running, add the lemon juice, and mix for 10 seconds.

Remove the mayonnaise from the food processor and store in refrigerator for up to 4 days.