Instructions: In a bowl, combine lemon juice and champagne vinegar.

In a separate glass bowl, whisk together egg yolk and dry ingredients.

Add half of the lemon juice mixture to the dry ingredients. Mix well before adding any oil. Begin adding oil, a little at a time, until it is incorporated into the emulsion. The color should lighten once 1/4 of the oil is emulsified. Then add the oil in a slow constant stream, whisking continuously. After 3/4 of the oil is incorporated, add the rest of the lemon juice mixture.

Continue to whisk until all of the oil is incorporated. Leave at room temperature for 1 hour. Refrigerate, covered, for up to 1 week.

Serve one teaspoon mayonnaise on top of chilled clams on the half shell.

This recipe yields 4 to 6 servings.

Variations: Add 1 tablespoon of any of the following ingredients: roasted garlic, basil chiffonade, chopped chipotle peppers, finely diced roasted red peppers, or prepared horseradish to one cup of mayonnaise.

Caution: The American Egg Board states: "There have been warnings against consuming raw or lightly cooked eggs on the grounds that the egg may be contaminated with Salmonella, a bacteria responsible for a type of foodborne illness. Healthy people need to remember that there is a very small risk and treat eggs and other raw animal foods accordingly. Use only properly refrigerated, clean, sound-shelled, fresh, grade AA or A eggs. Avoid mixing yolks and whites with the shell."

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