Break and separate eggs. We will only need the yolks. (We can use the whites in some sugar free desserts like the Floating Islands)
Get the oil ready by pouring it into a measuring jug. (In case of olive oil use only virgin and NOT extra virgin olive oil because extra virgin olive oil has a very strong flavor). Add the mustard to the egg yolks. We can use an empty jar for this or our favorite mixing bowl. The advantage of the jar is that we don't mess around that much with bowls and a lid can be put on it when it's done. However, the jar requires a bit of practice as it can spin around if the beater touches the side of the jar.
Whisk yolks in a mixing bowl. Pour oil very slowly into the bowl of whisked yolks. Pour only a few drops at a time whilst whisking constantly. With a bit of luck it will thicken eventually. When it is thickened we can pour the oil a bit faster but still in a slow and steady stream. When half of the oil is poured in the mayo should be nice and thick. If it isn't thick by now then the mayo has failed. Get a clean set of tools and try again. The failed creation can be incorporated into the successful attempts later.
Add the lemon juice and salt. Enjoy the whitening magic lemon juice does to the mayo. Optionally, if we are looking for a shop like mayonnaise flavor pour in some sweetener too.
Keep whisking and adding the second half of the oil until the end. In case we have any failed attempts that didn't thicken or broke up then this is the time to use it.
Keep homemade mayonnaise in the fridge refrigerated in an airtight container like the jar we have just used. Use it for about 6 days.