Name: Potatoes Lyonaise
Ingredients: 1 small onion, finely chopped; 2 to 3 tablespoons butter; cold boiled potatoes, cut into cubes; pepper, to taste; coarse sea salt, to taste; 1 tablespoon parsley, chopped

Why it works: Pepper and parsley match in chemistry and in kitchens. They rank in the top 2% of all ingredient pairs, and cooks put them together in 34,122 recipes. Both carry 4'-methylacetophenone, which smells bitter almond. The science ↓

Potatoes Lyonaise

Ingredients

1 small onion, finely chopped
2 to 3 tablespoons butter
cold boiled potatoes, cut into cubes
pepper, to taste
coarse sea salt, to taste
1 tablespoon parsley, chopped

Directions

Fry the chopped onion in butter until it begins to color.
Add the cold boiled potato cubes and stir gently with a fork.
Season with pepper and salt, and heat through.
Scatter the chopped parsley over the potatoes and cook for 2 to 3 minutes longer.
Serve immediately on a hot dish.

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.

Pepper + parsleytop 2% of all pairs

Smell alikestrong

Cooked together34,122 recipes

Shared aroma: 4'-methylacetophenone (bitter almond).
Onion + potatotop 3% of all pairs

Smell alikemoderate

Cooked together9,023 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Potato + parsleytop 5% of all pairs

Smell alikemoderate

Cooked together2,855 recipes

Shared aroma: 4'-methylacetophenone (bitter almond).
Onion + parsleytop 9% of all pairs

Smell alikemoderate

Cooked together25,843 recipes

Shared aroma: 2,4-decadienal (seaweed).
Potato + peppertop 9% of all pairs

Smell alikemoderate

Cooked together8,305 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).

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

What each ingredient does

Onion: Softens and browns in the butter, adding sweetness and savory depth to the potatoes.
Butter: Fat that fries the onion and coats the potatoes, adding richness and helping them brown.
Cold boiled potatoes: Form the body of the dish; cooking them cold lets the cubes hold their shape and crisp in the fat.

The step that matters

Stirring the potatoes gently with a fork. Potato cubes that are handled roughly break apart and turn mushy. Gentle stirring keeps the pieces intact so their surfaces can make contact with the hot fat and brown rather than steam.

Swap the onion

How well each one fits the dish's main ingredients (butter, potato, pepper, parsley):

Carrotfits better
Chivefits better
Capsicumfits better
Onionthe original

Fit is the average pairing score against butter, potato, pepper, parsley. 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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Potatoes Lyonaise