Name: Onion Soup
Ingredients: 10-12 large Spanish onions; ½ cup milk; ½ cup water; 1 old fowl, cut in pieces; 2 blades of mace; ½ cup cream; cayenne pepper, to taste; coarse sea salt, to taste; a few heads of asparagus

Why it works: Onion and asparagus match in chemistry and in kitchens. They rank in the top 9% of all ingredient pairs, and cooks put them together in 1,212 recipes. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓

Onion Soup

Ingredients

Directions

Prepare the onions

Boil the onions in milk and water, changing the liquid three times, until soft.
Rub the cooked onions through a fine sieve.

Make the gravy

Boil the fowl pieces with mace to make gravy, then strain it.

Combine and finish

Combine the onion pulp with the strained gravy and boil gently.
Add the grated crumb of an old penny loaf and cream, stirring until combined.
Season with cayenne pepper and salt to taste, then add asparagus.

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 + asparagustop 9% of all pairs

Smell alikestrong

Cooked together1,212 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Pepper + asparagustop 10% of all pairs

Smell alikemoderate

Cooked together1,968 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Onion + peppertop 11% of all pairs

Smell alikemoderate

Cooked together68,474 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Mace + peppertop 16% of all pairs

Smell alikelow

Cooked together12,257 recipes

Shared aroma: myristicin (spice, warm).
Milk + asparagustop 16% of all pairs

Smell alikemoderate

Cooked together650 recipes

Shared aroma: 1-octen-3-one (mushroom, metallic).

Mace and pepper barely smell alike, yet cooks put them together in 12,257 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

Spanish onions: Form the main body of the soup, becoming sweet and smooth when cooked and sieved.
Fowl: Gives the gravy its savoury meat flavour and body as it simmers.
Cream: Adds richness and a smoother, silkier texture to the finished soup.
Asparagus: Adds a fresh green vegetable flavour and texture at the end.

Swap the mace

How well each one fits the dish's main ingredients (onion, milk, cream, pepper, asparagus):

Garlicfits better
Celeryfits better
Tarragonfits better
Macethe original

Fit is the average pairing score against onion, milk, cream, pepper, asparagus. 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.