Place the egg yolks, 1 tsp of the lemon juice, the mustard and the pinch of salt in a bowl or in the bowl of your food processor or blender.
Start whisking/blending everything together and then start slowly drizzling the oil in.
Continue pouring in the oil slowly, but steadily. An emulsion will eventually start to form and you’ll be able to pour in the oil more quickly.
Using a blender, immersion blender or food processor make it very easy, but if you decide to whisk it by hand you’ll have to whisk quite vigorously for the whole process to prevent the mayonnaise from separating.
Your mayonnaise should be quite thick when all the oil is incorporated and you can then add the remaining lemon juice and blend it in with the mayonnaise.