To make mayonnaise, place 1 egg yolk in a food processor, add 1/8 teaspoon salt, and pulse to combine. Add 1/2 teaspoon Dijon mustard and 1 tablespoon lemon juice, and blend the mixture. Add 3/4 cup vegetable oil. Let the oil drip through the small hole in the feed-tube. Sample the mayo, and add lemon juice or more salt to taste. Refrigerate the covered mayonnaise for up to five days, and stir before spreading.
Alternatively, place 2 egg yolks in a food processor, and add 1 tablespoon Dijon mustard and 1/4 cup red wine vinegar. Using kosher salt, season the mixture to taste. Turn on the machine, and drizzle in 1 1/2 cups neutral-flavored oil slowly until the mixture resembles mayonnaise. Add a slow, steady stream of oil. For a thick mayonnaise, add a few drops of water. For a less thick mayonnaise, add a few drops of oil.
Similarly, place 2 large pasteurized egg yolks in a food processor, and add 4 teaspoons of fresh lemon juice and 1 teaspoon Dijon mustard. Pulse the ingredients to combine them. Turn on the motor, and add a slow, steady stream of oil. Season with coarse salt and ground pepper. If the mixture breaks, slowly add an egg yolk and 1 teaspoon tepid water to the broken mayonnaise while whisking.