Name: Onion Soup with Milk
Ingredients: 2 large onions, sliced; 2 tablespoons dripping or lard; 2 tablespoons flour; 1 quart boiling milk; Salt, to taste; Pepper, to taste; Any cold cooked vegetables, optional

Why it works: Onion and pepper are a kitchen classic. They rank in the top 11% of all ingredient pairs, and cooks put them together in 68,474 recipes. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓

Onion Soup with Milk

Ingredients

Directions

In a stew pan, heat the dripping or lard over medium heat.
Add the sliced onions and cook until browned.
Stir in the flour and cook for another minute.
Pour in the boiling milk and add salt and pepper.
If using, add any cold cooked vegetables.
Simmer for a few minutes, then serve hot.

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 + peppertop 11% of all pairs

Smell alikemoderate

Cooked together68,474 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Flour + milktop 14% of all pairs

Smell alikelow

Cooked together78,219 recipes

Shared aroma: isobutyraldehyde (malty, green).
Onion + flourtop 17% of all pairs

Smell alikemoderate

Cooked together32,460 recipes

Shared aroma: isobutyraldehyde (malty, green).
Flour + peppertop 19% of all pairs

Smell alikemoderate

Cooked together50,459 recipes

Shared aroma: isobutyraldehyde (malty, green).
Onion + milktop 20% of all pairs

Smell alikemoderate

Cooked together13,418 recipes

Shared aroma: hexanal (green, grassy).

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

Onions: Browning in the fat builds sweet, savoury flavour as the onions caramelise.
Flour: Thickens the milk into a smooth, lightly body soup as it cooks.
Milk: Forms the liquid base and adds creaminess and richness to the soup.
Dripping or lard: Carries the heat and fat that brown the onions and adds savoury flavour.

The step that matters

Stir in the flour and cook for another minute. Cooking the flour in the fat before adding liquid removes its raw taste and helps prevent lumps, so the soup thickens smoothly when the milk goes in.

Swap the onion

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

Capsicumfits better
Arrowrootfits better
Potatofits better
Onionthe original

Fit is the average pairing score against flour, milk, pepper. 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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Onion Soup with Milk