Homemade Mayonnaise

Egg yolk, acid, mustard and oil whisked into an emulsion. This is plain homemade mayonnaise; the keto framing in the source's title refers to a diet rather than to anything in the recipe, since mayonnaise is naturally low in carbohydrate whether or not anyone is counting. Emulsification is the whole technique. The lecithin in egg yolk allows oil and an acidic liquid, which do not mix, to hold together as a stable suspension, and that only happens if the oil goes in slowly enough for each addition to be absorbed. A few drops at a time to begin with, then a thin stream once it thickens. Poured in quickly it splits, and a split mayonnaise can be rescued by starting again with a fresh yolk and whisking the broken mixture into it drop by drop. **This contains raw egg yolk and is not cooked at any point.** That matters for anyone pregnant, elderly, very young or immunocompromised, and pasteurised eggs are the sensible answer if you are serving it to any of them. It keeps a week refrigerated. Use a light oil rather than extra virgin olive oil, which turns bitter when whisked hard.