In a mixing bowl, using a wooden spatula mix the boiled egg with the raw egg until you get a paste.
Add a couple drops lemon juice, 2-3 drops oil and mix by hand until fully incorporated.
Add a few more drops of lemon juice and about a tablespoon oil and continue mixing by hand until the mixture doubles in size.
At this point you can switch to a hand mixer but continue adding lemon juice and oil a little at a time until both are done.
Finish with a teaspoon of mustard and salt to taste and mix until fully incorporated.
Tip: At any point, if the mayonnaise separates after the oil is added and the mixture has broken, add an egg yolk and 1 teaspoon tepid water then continue mixing by hand. Or add the mustard, a little at a time, until the mixture is back to normal. Using the lemon juice from the very start should prevent this from happening but accidents do occur sometimes.
Enjoy this homemade mayonnaise recipe with your sandwiches, burgers, wraps or even salads, sauces or dips!