1 large local egg yolk, room temperature
1/8 teaspoon salt, plus more to taste
1 tablespoon lemon juice, plus more to taste
1/2 teaspoon Dijon mustard
3/4 cup vegetable oil/walnut oil/olive oil (olive oil will have flavor of olives)
1. Either blend egg yolk and salt lemon juice and Dijon mustard and whisk together with oil drop by drop or place the egg yolk and salt in a food processor. Pulse to combine. Add the lemon juice and mustard; blend well. With the motor running, add the oil, drop by drop. This will take a few minutes. Don't rush it or the mayonnaise may "break," meaning the oil will separate from the egg. (Note: If your food processor has a small hole in the feed-tube pusher, pour the oil in there and let it drip through.)
2. Once you've added the oil, sample the mayo and add more salt or lemon juice to taste. Cover tightly and refrigerate for up to 5 days. Stir before spreading.