Add chopped garlic, anchovies, egg yolk, white balsamic vinegar and lemon juice to a small bowl and whisk together until well combined. Slowly stream in the olive oil while continuing to whisk until fully emulsified. Taste, season with a pinch of salt and add a little more lemon juice if you wish. To thin, add water a tablespoon at a time until the consistency is right for you. Transfer to a sealable storage jar and keep in the fridge for up to 2 weeks.