Name: Welsh Sauce
Ingredients: 1 tablespoon chopped parsley; 1 teaspoon chopped onion; 3 tablespoons cream; cayenne pepper to taste; black pepper to taste; coarse sea salt to taste; 1 teaspoon tarragon vinegar; 1 tablespoon salad oil

Why it works: Parsley and tarragon match in chemistry and in kitchens. They rank in the top 1% of all ingredient pairs, and cooks put them together in 1,563 recipes. Both carry estragole, which smells anise, licorice. The science ↓

Welsh Sauce

Ingredients

Directions

In a bowl, combine chopped parsley, chopped onion, cream, cayenne pepper, black pepper, and coarse sea salt, then mix well.
Add tarragon vinegar and salad oil last, and mix again.

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.

Parsley + tarragontop 1% of all pairs

Smell alikestrong

Cooked together1,563 recipes

Shared aroma: estragole (anise, licorice).
Parsley + peppertop 2% of all pairs

Smell alikestrong

Cooked together34,122 recipes

Shared aroma: 4'-methylacetophenone (bitter almond).
Pepper + tarragontop 5% of all pairs

Smell alikestrong

Cooked together2,399 recipes

Shared aroma: estragole (anise, licorice).
Tarragon + vinegartop 7% of all pairs

Smell alikemoderate

Cooked together2,547 recipes

Shared aroma: isobutyraldehyde (malty, green).
Parsley + oniontop 9% of all pairs

Smell alikemoderate

Cooked together25,843 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

Cream: Provides the creamy body and moisture that carries the other flavours in the sauce.
Tarragon vinegar: Adds a sharp acidity that brightens the cream and balances its richness.
Salad oil: Adds fat that gives the sauce a smoother, silkier mouthfeel.

Swap the onion

How well each one fits the dish's main ingredients (parsley, cream, pepper, tarragon, vinegar):

Shallotfits better
Mustardfits better
Lettucefits better
Onionthe original

Fit is the average pairing score against parsley, cream, pepper, tarragon, vinegar. 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.