In a food processor, pulse together the egg yolks, 1 teaspoon warm water, the mustard, and lemon juice.

With the blade running, drizzle in the oil in a medium stream. If the mixture becomes too thick before all of the oil has been incorporated, add a drop or two of warm water to loosen the mixture, then continue with the remaining oil. Season with salt and pepper and store, refrigerated, in a covered plastic or noncorrosive metal container.

Variation:

To make aioli, add 6 garlic cloves, chopped, along with the egg yolks. Season with coarse black pepper.