Why it works: Bread and butter are a kitchen classic. They rank in the top 7% of all ingredient pairs, and cooks put them together in 27,232 recipes. Both carry delta-decalactone, which smells sweet, creamy. The science ↓
Potato Gratin
Ingredients
Directions
The book says “a moderately quick oven”. The 350°F (175°C) in the steps is the modern equivalent, not the book's own figure.
Make the sauce
In a saucepan, melt the butter and stir in the flour until smooth.
Gradually pour in the milk, stirring constantly until boiling.
Add salt and pepper to the sauce.
Assemble and bake
In a baking dish, layer some sauce, then a layer of potatoes, repeating until all are used, finishing with sauce on top.
Sprinkle the bread crumbs over the top.
Cover the baking dish and bake at 350°F (175°C) for 15 minutes, then uncover and bake until the potatoes are tender and the top is browned.
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.
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Bread + buttertop 7% of all pairsSmell alikemoderateCooked together27,232 recipes
Shared aroma: delta-decalactone (sweet, creamy).
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Butter + milktop 7% of all pairsSmell alikemoderateCooked together81,283 recipes
Shared aroma: (z)-4-heptenal (biscuit, cream).
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Potato + peppertop 9% of all pairsSmell alikemoderateCooked together8,305 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Potato + milktop 9% of all pairsSmell alikemoderateCooked together3,611 recipes
Shared aroma: (e,z)-2,6-nonadienal (cucumber, melon).
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Bread + milktop 11% of all pairsSmell alikemoderateCooked together11,466 recipes
Shared aroma: 2-undecenal (sweet).
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
What each ingredient does
- Potatoes
- Form the bulk of the dish and become tender and soft during baking.
- Flour
- Thickens the butter and milk into a smooth, body-rich white sauce.
- Milk
- Forms the liquid base of the sauce that coats and moistens the potatoes.
- Butter
- Enriches the sauce and helps the flour cook into a smooth roux.
- Stale bread crumbs
- Form a crisp topping that browns in the oven.
The step that matters
Bringing the sauce to a boil while stirring constantly. Flour must be cooked in the hot butter and milk until the mixture boils and thickens; otherwise the sauce stays floury or can lump, and the sauce then cannot thicken properly around the potatoes.
Swap the potato
How well each one fits the dish's main ingredients (bread, butter, flour, milk, pepper):
- Capsicumfits about as well
- Potatothe original
- Shallotfits about as well
- Leekfits about as well
Fit is the average pairing score against bread, butter, 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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