Why it works: Mustard and onion 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 ↓
Mayonnaise
Ingredients
Directions
Prepare
Rub the inside of a bowl with a slice of onion.
Beat the egg yolks with the dry mustard, sugar, and salt.
Make the emulsion
Slowly beat in the olive oil, adding just a drop or two at a time while stirring in one direction.
Once the mixture thickens, you can add the oil in larger quantities.
Rescue a separated mayonnaise
If the mixture separates, chill it in the refrigerator for 15-20 minutes and try again.
If it still won't mix, add the yolk of another very cold egg.
If necessary, start over with chilled ingredients and utensils.
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.
Photo for illustrative purposes only · Contact us to use it
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 + oniontop 6% of all pairsSmell alikestrongCooked together9,259 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Mustard + vinegartop 7% of all pairsSmell alikemoderateCooked together14,067 recipes
Shared aroma: isobutyraldehyde (malty, green).
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Lemon + olivetop 7% of all pairsSmell alikemoderateCooked together11,922 recipes
Shared aroma: 3-hexenal (apple, fruity).
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Mustard + olivetop 8% of all pairsSmell alikestrongCooked together5,950 recipes
Shared aroma: eucalyptol (eucalyptus, herbal).
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Olive + oniontop 8% of all pairsSmell alikemoderateCooked together29,779 recipes
Shared aroma: 2,4-decadienal (seaweed).
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
What each ingredient does
- Egg yolks
- Lecithin in the yolk emulsifies the oil and water, holding the sauce together and giving it body.
- Olive oil
- Forms the bulk of the sauce, providing richness and a thick, fatty texture as it is dispersed into droplets.
- Dry mustard
- Its compounds help stabilise the emulsion, making it less likely to break.
- Vinegar
- Adds acidity that brightens the flavour and balances the richness of the oil.
- Lemon juice
- Adds acidity and fresh flavour that cuts through the richness of the oil.
The step that matters
Adding the oil slowly at the start. The first oil must be dispersed as tiny droplets in the yolk. Adding it too fast overwhelms the yolk's emulsifiers, so the oil separates instead of thickening into a stable sauce.
Swap the onion
How well each one fits the dish's main ingredients (egg, mustard, sugar, vinegar, lemon, olive):
- Horseradishfits better
- Shallotfits better
- Broccolifits better
- Onionthe original
Fit is the average pairing score against egg, mustard, sugar, vinegar, lemon, olive. 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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