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Morcan’s Tartan Sauce—to Mix Mustard

A mustard-based tartan sauce with cucumber pickles, capers, parsley, and shallot, thickened with sweet oil and egg yolk.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 11 ingredients
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Why it works: Capers and shallot match in chemistry and in kitchens. They rank in the top 1% of all ingredient pairs, and cooks put them together in 405 recipes. Both carry coumarin, which smells sweet, hay. The science ↓

Morcan’s Tartan Sauce—to Mix Mustard

Ingredients

Directions

Make the emulsion

  1. In a bowl, combine mustard, salt, and cayenne pepper.

  2. Add the yolk of the raw egg and mix well.

  3. Slowly add sweet oil, stirring until thick.

  4. Thin the mixture with a little vinegar.

Finish the sauce

  1. Chop the cucumber pickles, capers, parsley, and shallot or leek finely.

  2. Stir the chopped ingredients into the sauce about an hour before serving.

  3. If the sauce is too thick, add cold water to reach desired consistency.

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. Capers + shallottop 1% of all pairs
    Smell alikestrong
    Cooked together405 recipes

    Shared aroma: coumarin (sweet, hay).

  2. Mustard + caperstop 1% of all pairs
    Smell alikestrong
    Cooked together624 recipes

    Shared aroma: coumarin (sweet, hay).

  3. Mustard + shallottop 1% of all pairs
    Smell alikestrong
    Cooked together859 recipes

    Shared aroma: eucalyptol (eucalyptus, herbal).

  4. Capers + parsleytop 1% of all pairs
    Smell alikestrong
    Cooked together1,550 recipes

    Shared aroma: coumarin (sweet, hay).

  5. Parsley + shallottop 1% of all pairs
    Smell alikestrong
    Cooked together3,737 recipes

    Shared aroma: 2,4-decadienal (seaweed).

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

What each ingredient does

Raw egg yolk
Binds the oil and mustard into a thick, stable emulsion.
Sweet oil
Provides the fat that gives the sauce its rich body and thickness.
Mixed mustard
Helps hold the emulsion together and adds sharp flavour.
Vinegar
Adds acidity to brighten the sauce and thins it to the right texture.
Cucumber pickles
Adds crunch and sour, tangy flavour through the sauce.

The step that matters

Adding the oil slowly. Oil must be added gradually while stirring so the egg yolk can emulsify it. Adding it too fast causes the sauce to split and stay oily instead of thickening.

Swap the cucumber

How well each one fits the dish's main ingredients (mustard, pepper, egg, vinegar, capers, parsley, shallot):

  1. Horseradishfits better
  2. Chivefits better
  3. Kalefits better
  4. Cucumberthe original

Fit is the average pairing score against mustard, pepper, egg, vinegar, capers, parsley, shallot. 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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