Why it works: Mustard and capers match in chemistry and in kitchens. They rank in the top 1% of all ingredient pairs, and cooks put them together in 624 recipes. Both carry coumarin, which smells sweet, hay. The science ↓
Butter Sauce, Tartare
Ingredients
Directions
Make the sauce
In a bowl, combine the butter sauce, onion juice, mustard mixed with vinegar, gherkins, capers, and beaten egg.
Stir gently to combine.
Remove the sauce from heat immediately after mixing.
Serve
Serve with fish.
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.
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Mustard + caperstop 1% of all pairsSmell alikestrongCooked together624 recipes
Shared aroma: coumarin (sweet, hay).
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Onion + mustardtop 6% of all pairsSmell alikestrongCooked together9,259 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Onion + caperstop 7% of all pairsSmell alikestrongCooked together1,381 recipes
Shared aroma: coumarin (sweet, hay).
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Mustard + vinegartop 7% of all pairsSmell alikemoderateCooked together14,067 recipes
Shared aroma: isobutyraldehyde (malty, green).
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Sauce + caperstop 11% of all pairsSmell alikemoderateCooked together678 recipes
Shared aroma: ethanol (alcoholic, ethereal).
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
What each ingredient does
- Butter sauce
- Forms the rich, creamy base of the sauce.
- Beaten egg
- Adds richness and body, helping the sauce thicken as it warms.
- Gherkins
- Add a sharp, briny bite that cuts through the richness.
- Capers
- Add a salty, tangy bite that balances the butter.
- Vinegar
- Adds acidity that brightens the sauce and sharpens the flavour.
- Onion juice
- Adds a savoury aroma and background sharpness.
The step that matters
Remove the sauce from heat immediately after mixing. Egg proteins set when heated, so lingering heat after the beaten egg is added can scramble it and leave the sauce grainy instead of smooth.
Swap the onion
How well each one fits the dish's main ingredients (butter, sauce, mustard, vinegar, capers, egg):
- Shallotfits better
- Horseradishfits better
- Chivefits better
- Onionthe original
Fit is the average pairing score against butter, sauce, mustard, vinegar, capers, egg. 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.
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