Name: Caviar Sandwich
Ingredients: bread; mustard butter; caviar; lettuce leaves; hard-boiled egg yolk, finely chopped; onion, very finely chopped; chives, finely chopped; lemons or limes

Why it works: Mustard and lettuce match in chemistry and in kitchens. They rank in the top 1% of all ingredient pairs, and cooks put them together in 1,356 recipes. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓

Caviar Sandwich

Ingredients

Directions

Spread mustard butter on slices of bread.
Top with a layer of caviar.
Cut the sandwiches into desired shapes.
Arrange on a platter with lettuce leaves.
Garnish one leaf with chopped egg yolk, another with chopped onions, and another with chopped chives.
Serve with lemon or lime, cut into halves or quarters.

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.

Mustard + lettucetop 1% of all pairs

Smell alikestrong

Cooked together1,356 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Lettuce + chivetop 1% of all pairs

Smell alikestrong

Cooked together261 recipes

Shared aroma: coumarin (sweet, hay).
Mustard + chivetop 1% of all pairs

Smell alikestrong

Cooked together587 recipes

Shared aroma: guaiacol (smoky, sweet).
Onion + chivetop 3% of all pairs

Smell alikestrong

Cooked together1,907 recipes

Shared aroma: decanal (soap, orange peel).
Mustard + oniontop 6% of all pairs

Smell alikestrong

Cooked together9,259 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).

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

Swap the onion

How well each one fits the dish's main ingredients (bread, mustard, butter, caviar, lettuce, egg, chive):

Shallotfits better
Cucumberfits better
Asparagusfits better
Onionthe original

Fit is the average pairing score against bread, mustard, butter, caviar, lettuce, egg, chive. Candidates are from the same food group and used in at least 100 recipes.