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Sauce Robert

A French brown onion sauce made with butter, flour, gravy, mustard, salt, and pepper.

From an old cookbook · modernised transcription
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Why it works: Onion and mustard match in chemistry and in kitchens. They rank in the top 6% of all ingredient pairs, and cooks put them together in 9,259 recipes. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓

Sauce Robert

Ingredients

Directions

Prepare

  1. Dice the onions into small pieces.

Make the sauce

  1. Brown the onions in a saucepan with the butter.

  2. Once browned, add the flour and stir until combined.

  3. Pour in the gravy and let it simmer for 15 minutes.

  4. Skim the sauce, then season with salt and pepper.

  5. Just before serving, mix in the prepared mustard.

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.

  1. Onion + mustardtop 6% of all pairs
    Smell alikestrong
    Cooked together9,259 recipes

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

  2. Onion + beeftop 7% of all pairs
    Smell alikemoderate
    Cooked together17,092 recipes

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

  3. Pepper + mustardtop 9% of all pairs
    Smell alikemoderate
    Cooked together15,430 recipes

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

  4. Beef + peppertop 10% of all pairs
    Smell alikemoderate
    Cooked together18,971 recipes

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

  5. 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
Browned onions give the sauce its deep, sweet, savoury base flavour.
Butter
Fat for browning the onions, adding richness and flavour to the sauce.
Flour
Thickens the gravy into a smooth sauce body once cooked through.
Beef or veal gravy
Forms the liquid base of the sauce, providing meaty flavour and moisture.
Prepared mustard
Adds sharpness and a tangy bite that balances the rich sauce.

The step that matters

Brown the onions in the butter. Onions that are only softened, not browned, lack the caramelised sweetness and colour the sauce needs. Browning relies on dry, moderate heat and stirring so the sugars brown without burning, which would make the sauce bitter.

Swap the mustard

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

  1. Potatofits better
  2. Chivefits better
  3. Leekfits better
  4. Mustardthe original

Fit is the average pairing score against onion, butter, flour, beef, 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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