Homemade mayonnaise sounds like a really unnecessary thing...until you realize that it takes less time to make it than to go to the store if you have run out. That is exactly what happened...we were in the midst of making lunch and realized that mayo was a crucial ingredient and we did not have any.
All you need is an egg yolk and some olive oil, a pinch of salt and a squeeze of lemon juice or dash of vinegar. I also added some minced shallots but that is not at all necessary.
1 egg yolk
a generous pinch of salt
1/2 teaspoon dijon mustard
1 teaspoon minced shallot (optional)
Juice of 1 lemon
about 1/2 cup extra virgin olive oil (you can use up to 1 cup of oil per yolk if you need more mayonnaise)
Place yolk, salt, mustard and shallot in a bowl and whisk to combine. Add a squeeze of lemon juice and whisk. While still whisking, slowly drizzle in olive oil, a few drops at a time, to emulsify. Once the mayonnaise starts to have a nice thick creamy consistency you can add the oil slightly more quickly but make sure that it is all getting incorporated. Taste and add more lemon juice and salt as desired.