Name: Lentil Soup
Ingredients: 1 quart Egyptian red lentils; 4 quarts water; 2 pounds turnips; 1 pound carrots; 1 Spanish onion; 1 root celery; 1 ounce parsley; coarse sea salt to taste; 1 ounce Nutcoa or butter

Why it works: Lentils and turnip match in chemistry and in kitchens. They rank in the top 1% of all ingredient pairs, and cooks put them together in 109 recipes. Both carry coumarin, which smells sweet, hay. The science ↓

Lentil Soup

Ingredients

Directions

Prepare

Wash and pick over the lentils.
In a large pot, combine lentils and water.

Cook and strain

Add turnips, carrots, onion, celery, parsley, and salt.
Boil until soft, then rub through a fine colander, adding boiling water as needed.

Finish

Return to the pot, season, and add Nutcoa or butter.
Boil for a few more minutes.

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.

Lentils + turniptop 1% of all pairs

Smell alikestrong

Cooked together109 recipes

Shared aroma: coumarin (sweet, hay).
Carrot + parsleytop 1% of all pairs

Smell alikestrong

Cooked together8,053 recipes

Shared aroma: 2,4-decadienal (seaweed).
Carrot + celerytop 1% of all pairs

Smell alikestrong

Cooked together10,173 recipes

Shared aroma: myristicin (spice, warm).
Turnip + carrottop 1% of all pairs

Smell alikestrong

Cooked together8,002 recipes

Shared aroma: coumarin (sweet, hay).
Celery + parsleytop 1% of all pairs

Smell alikestrong

Cooked together6,810 recipes

Shared aroma: 4'-methylacetophenone (bitter almond).

Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs

What each ingredient does

Egyptian red lentils: Break down during boiling to thicken the soup into a smooth body.
Turnips: Add body and a mild, earthy sweetness as they soften in the broth.
Carrots: Contribute sweetness and color, softening as they cook.
Nutcoa or butter: Adds richness and fat, giving the soup a smoother mouthfeel and rounder flavor.

The step that matters

Rub through a fine colander. The soup must be pushed through while the vegetables and lentils are fully soft. Undercooked pieces will not pass through the colander, leaving a grainy texture. Adding boiling water keeps the purée loose and prevents it from thickening too much as it cools.

Swap the onion

How well each one fits the dish's main ingredients (lentils, turnip, carrot, celery, parsley, butter):

Parsnipfits better
Leekfits better
Kalefits better
Onionthe original

Fit is the average pairing score against lentils, turnip, carrot, celery, parsley, butter. 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.