Put the garlic, egg yolks and a pinch of salt into a 900ml basin with a narrow base. Mix well using a metal spoon. Using an electric whisk gradually add the oil one drop at a time, whisking thoroughly between each addition. Once about half of the oil is added, start to add drops of lemon juice. When the mixture begins to thicken you can begin to add slightly more oil at a time. The mixture should become thick and well combined. Stir in the boiling water to prevent the mayo from seperating.