Why it works: Peas and onion are a kitchen classic. They rank in the top 13% of all ingredient pairs, and cooks put them together in 5,460 recipes. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓
Pea Soup
Ingredients
Directions
Make the soup
Put the peas and onion into a soup pot.
Pour in enough water to cover and boil for 45 minutes.
Mash the mixture through a colander and add 1 pint of water.
Make the cream base and finish
In a separate pan, cook the flour in the oil until light brown.
Add the milk, cream, and salt to the flour mixture.
Pour this into the soup, boil for a few minutes, and serve.
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.
-
Peas + oniontop 13% of all pairsSmell alikemoderateCooked together5,460 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
-
Flour + milktop 14% of all pairsSmell alikelowCooked together78,219 recipes
Shared aroma: isobutyraldehyde (malty, green).
-
Peas + milktop 16% of all pairsSmell alikemoderateCooked together1,309 recipes
Shared aroma: hexanal (green, grassy).
-
Onion + flourtop 17% of all pairsSmell alikemoderateCooked together32,460 recipes
Shared aroma: isobutyraldehyde (malty, green).
-
Milk + creamtop 18% of all pairsSmell alikemoderateCooked together29,399 recipes
Shared aroma: delta-dodecalactone (sweet, creamy).
Flour and milk barely smell alike, yet cooks put them together in 78,219 recipes: they work on texture and structure more than aroma.
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
What each ingredient does
- Green peas
- Form the bulk of the soup and give it its body and flavour.
- Flour
- Thickens the cream mixture when cooked in oil until lightly browned.
- Milk
- Adds moisture and softness, mellowing the soup's texture.
- Cream
- Adds richness and a smoother, fuller mouthfeel to the soup.
The step that matters
Cooking the flour in oil until light brown. Cooking flour in fat first toasts the starch and removes raw flour taste, and it thickens more evenly when the liquid is added. Stop at light brown so the roux does not taste bitter or lose thickening power.
Swap the peas
How well each one fits the dish's main ingredients (onion, flour, milk, cream):
- Almondfits better
- Cashew nutfits better
- Chestnutfits better
- Peasthe original
Fit is the average pairing score against onion, flour, milk, cream. 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.
More pea soup recipes
You might also like
The free Flavor Lab newsletter: one surprising pairing a week and the molecular reason it works, in 60 seconds. No spam, unsubscribe anytime.
Prefer an account? Create a free account to save pairings and unlock the full chemistry.

Green Peas229 recipes
Green Peas Soup35 recipes
Tomato Soup526 recipes
Brown Bread461 recipes