Name: Onions to Pickle
Ingredients: small onions; coarse sea salt; boiling water; boiling cider vinegar; whole peppercorns; mustard

Why it works: Onion and mustard match in chemistry and in kitchens. They rank in the top 6% of all ingredient pairs, and cooks put them together in 9,259 recipes. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓

Onions to Pickle

Ingredients

Directions

Peel and wash the small onions, trying to keep them as uniform in size as possible.
Sprinkle the onions generously with coarse sea salt.
Pour boiling water over the onions to cover them, stirring to dissolve the salt.
Cover and let the onions stand for 24 hours.
Transfer the onions to jars and pour boiling cider vinegar over them, adding whole peppercorns and mustard before boiling.

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.

Onion + mustardtop 6% of all pairs

Smell alikestrong

Cooked together9,259 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Cider + vinegartop 6% of all pairs

Smell alikemoderate

Cooked together3,431 recipes

Shared aroma: 4-ethyl-2-methoxyphenol (smoky, clove).
Vinegar + mustardtop 7% of all pairs

Smell alikemoderate

Cooked together14,067 recipes

Shared aroma: isobutyraldehyde (malty, green).
Cider + mustardtop 13% of all pairs

Smell alikelow

Cooked together1,414 recipes

Shared aroma: linalool (floral, citrus).
Onion + vinegartop 14% of all pairs

Smell alikemoderate

Cooked together18,226 recipes

Shared aroma: acetic acid (sour, vinegar).