Name: Brown Onion Sauces, or Onion Gravy
Ingredients: 1 quart onions, peeled and sliced; 2 tablespoons butter; ½ ounce flour; 1 cup broth (or ½ cup water); ¼ teaspoon pepper; ¼ teaspoon salt; 1 tablespoon claret or port wine; 1 tablespoon mushroom ketchup; lemon juice or vinegar (optional)

Why it works: Pepper and lemon match in chemistry and in kitchens. They rank in the top 3% of all ingredient pairs, and cooks put them together in 27,047 recipes. Both carry trans-2-nonenal, which smells cardboard, fatty. The science ↓

Brown Onion Sauces, or Onion Gravy

Ingredients

Directions

Make the gravy

In a quart saucepan, melt the butter over low heat.
Add the sliced onions and cook until lightly browned.
Gradually stir in the flour.
Add the broth (or water), pepper, and salt; bring to a boil.
Stir in the claret (or port) and mushroom ketchup.
Rub the sauce through a fine sieve.

Serve

For steaks, add fried onions or whole boiled young onions before serving.

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 + lemontop 3% of all pairs

Smell alikestrong

Cooked together27,047 recipes

Shared aroma: trans-2-nonenal (cardboard, fatty).
Butter + mushroomtop 7% of all pairs

Smell alikemoderate

Cooked together12,525 recipes

Shared aroma: trans-2-decenal (waxy, orange).
Onion + mushroomtop 10% of all pairs

Smell alikemoderate

Cooked together10,626 recipes

Shared aroma: 2,4-decadienal (seaweed).
Port wine + mushroomtop 10% of all pairs

Smell alikemoderate

Cooked together570 recipes

Shared aroma: guaiacol (smoky, sweet).
Onion + peppertop 11% of all pairs

Smell alikemoderate

Cooked together68,474 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

Onions: Provide the main body and sweet, savoury flavour as they brown.
Butter: Carries flavour and adds richness to the gravy.
Flour: Thickens the broth into a smooth, lightly bodied gravy.
Broth: Forms the liquid base that the flour thickens.
Claret or port wine: Adds depth and a fruity, slightly acidic background note.

The step that matters

Gradually stir in the flour. Adding flour all at once to hot fat can form lumps that are hard to smooth out. Stirring it in gradually, while the onions and butter are hot, coats the flour evenly so it thickens the liquid smoothly later.

Swap the lemon

The recipe marks lemon as optional. How well each one fits the dish's main ingredients (onion, butter, flour, pepper, port wine, mushroom, ketchup):

Lemonthe original
Red currantfits about as well
Limefits about as well
Plumfits about as well

Fit is the average pairing score against onion, butter, flour, pepper, port wine, mushroom, ketchup. 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.

Lemon Sauce236 recipes

Mushroom Soup60 recipes

Tomato Soup526 recipes

Brown Bread461 recipes

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Brown Onion Sauces, or Onion Gravy