In the bowl of a food processor, combine the whole egg, the egg yolk, the salt and the mustard. Pulse a few times to mix. Turn the processor on and painfully, achingly, my-arm-is-gonna-fall-off slowly drizzle in a steady stream of the oil. (A thin strand of oil should fall from the bottle through the food shoot of the lid.) You’ll soon notice the mixture starts to make a “whap, whap, whap” sound (and, yes, that is the technical term for it). This is the oil and egg mixing together to create an emulsion. After about half of the oil has been added, pour in the vinegar and lemon juice. (I don’t know why, but I’ve had a problem getting the emulsion to form unless I wait until about mid-way through the mixing to add the acid.) Keep pouring in the oil until it’s all mixed in and voila…mayonnaise!
