For the mayonnaise, put the egg yolks, salt, pepper, lemon juice and mustard in a bowl and stir with a whisk or hand mixer until smooth. Let the oil run in slowly, at first only a few drops. When all the oil is used up, beat a little further.
When the mayonnaise is ready, press the garlic cloves one by one into the mayonnaise with a press and stir. Season to taste with the sherry. Goes well with tortilla, bread, seafood and meat.