Name: Lettuce Dressing
Ingredients: 3 egg yolks; ½ cup weak vinegar; 2 teaspoons sugar; ¼ cup melted butter; 1 teaspoon prepared mustard; salt to taste; pepper to taste

Why it works: Vinegar and mustard are a kitchen classic. They rank in the top 7% of all ingredient pairs, and cooks put them together in 14,067 recipes. Both carry isobutyraldehyde, which smells malty, green. The science ↓

Lettuce Dressing

Ingredients

Directions

Beat the yolks of the eggs until light.
Stir in the vinegar, sugar, and melted butter.
Cook in a double boiler, stirring constantly, until it thickens to custard consistency.
Add the mustard, salt, and pepper.
Thin with additional vinegar until it can pass through a sieve.
Adjust vinegar if too sharp for salads.

Recipe from a historical cookbook (Internet Archive).

Transcribed from a scanned cookbook and modernised for today's kitchens. Where the book gave no heat or time, or said "a moderate oven", the temperatures and times here may be modern equivalents rather than the book's own figures.

Explore the science

The flavor team

The pairs that carry this dish. Each one is judged two ways: how much their aromas overlap, and how often cooks already put them together.

Vinegar + mustardtop 7% of all pairs

Smell alikemoderate

Cooked together14,067 recipes

Shared aroma: isobutyraldehyde (malty, green).
Mustard + peppertop 9% of all pairs

Smell alikemoderate

Cooked together15,430 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Vinegar + peppertop 14% of all pairs

Smell alikemoderate

Cooked together27,814 recipes

Shared aroma: 4'-methylacetophenone (bitter almond).
Vinegar + sugartop 15% of all pairs

Smell alikemoderate

Cooked together20,806 recipes

Shared aroma: beta-damascenone (apple, rose).
Egg + buttertop 17% of all pairs

Smell alikemoderate

Cooked together118,967 recipes

Shared aroma: decanal (soap, orange peel).

Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs

What each ingredient does

Egg yolks: Thicken as they cook, forming a smooth custard-like emulsion that gives the dressing body.
Melted butter: Adds fat that enriches the dressing and gives it a rich, smooth mouthfeel.
Vinegar: Provides the sharp acidity that balances the richness of the yolks and butter.
Sugar: Softens the sharpness of the vinegar, adding gentle sweetness.
Prepared mustard: Adds a sharp, savory note and helps stabilize the emulsion.

The step that matters

Cook in a double boiler, stirring constantly, until it thickens to custard consistency. Egg yolks begin to set gently near 160°F, so heating slowly over simmering water while stirring keeps the custard smooth. Overheating scrambles the yolks into lumps.

Swap the mustard

How well each one fits the dish's main ingredients (egg, vinegar, sugar, butter, pepper):

Capsicumfits better
Mustardthe original
Cucumberfits about as well
Shallotfits less well

Fit is the average pairing score against egg, vinegar, sugar, butter, pepper. Candidates are from the same food group and used in at least 100 recipes.

“What each ingredient does” and “The step that matters” were written by Claude from this recipe’s own method and reviewed in samples by CompKitchen.