Name: Roast Beef Pie with Potato Crust
Ingredients: cold roast beef, sliced; gravy from the roast; 2 tablespoons butter; 1 onion, sliced; ¼ teaspoon black pepper; ¼ teaspoon coarse sea salt; water, as needed; 1 tablespoon all-purpose flour; potatoes, enough to fill the baking dish; milk, as needed; butter, as needed; 1 egg, beaten; tomato sauce or Worcestershire sauce, for serving

Why it works: Onion and potato are a kitchen classic. They rank in the top 3% of all ingredient pairs, and cooks put them together in 9,023 recipes. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓

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 + potatotop 3% of all pairs

Smell alikemoderate

Cooked together9,023 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Beef + oniontop 7% of all pairs

Smell alikemoderate

Cooked together17,092 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Butter + milktop 7% of all pairs

Smell alikemoderate

Cooked together81,283 recipes

Shared aroma: (z)-4-heptenal (biscuit, cream).
Beef + potatotop 8% of all pairs

Smell alikemoderate

Cooked together2,052 recipes

Shared aroma: sotolon (curry, maple).
Pepper + potatotop 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

Cold roast beef: Provides the main meat filling, which is already cooked and only needs warming through.
All-purpose flour: Thickens the gravy so it holds together rather than running out of the pie.
Potatoes: Form the mashed topping that covers the filling and bakes into a crust.
Egg: Brushed on top, it helps the potato crust brown and turn golden in the oven.
Butter: Adds richness and fat to the onion filling and the mashed potato topping.
Onion: Adds savory sweetness and aroma to the meat filling as it cooks gently.

The step that matters

Simmer the filling gently after adding flour. Flour thickens the gravy only when heated, but high heat can scorch it on the pan bottom. Gentle simmering lets the starch thicken evenly without burning, keeping the filling smooth and free of a bitter, burnt taste.

Swap the onion

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

Chivefits better
Asparagusfits better
Capsicumfits about as well
Onionthe original

Fit is the average pairing score against beef, butter, pepper, flour, potato, milk, egg. 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.

Roast Beef Pie with Potato Crust