Put a small splash of white vinegar in a bowl, add one egg yolk and some mustard. Stir those together until it starts to form bubbles on the surface. Then slowly start to add sunflower oil to it and keep stirring to make stir it all binds together. Once the mixture start to really bind you can start pouring the oil in a little faster and keep going until you think your mayonnaise has the right consistency. It's as easy as that!
Add finely chopped parsley, pepper, salt and lime to taste