Name: Green Butter with Herring Roes
Ingredients: ¼ pound fresh butter; 1 handful spinach; 2 soft herring roes; 1 large bunch curly parsley; 12 capers; pepper to taste

Why it works: Parsley and capers match in chemistry and in kitchens. They rank in the top 1% of all ingredient pairs, and cooks put them together in 1,550 recipes. Both carry coumarin, which smells sweet, hay. The science ↓

Green Butter with Herring Roes

Ingredients

Directions

Prepare

Set the cream to make fresh butter and chill it in ice.
Boil the spinach until tender, then squeeze it through muslin to save the pulp.
Dust the spinach pulp with pepper.
Wipe the herring roes to remove oil, then pound them in a mortar and pass through a fine sieve.
Mince the parsley and capers finely.

Make the butter

Mix all ingredients together with a wooden spoon.
Color the mixture with the spinach pulp, shape it as desired, and chill in ice until ready to serve.

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 + caperstop 1% of all pairs

Smell alikestrong

Cooked together1,550 recipes

Shared aroma: coumarin (sweet, hay).
Spinach + caperstop 1% of all pairs

Smell alikestrong

Cooked together99 recipes

Shared aroma: coumarin (sweet, hay).
Parsley + peppertop 2% of all pairs

Smell alikestrong

Cooked together34,122 recipes

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

Smell alikestrong

Cooked together1,025 recipes

Shared aroma: trans-2-hexenal (green, leafy).
Spinach + peppertop 6% of all pairs

Smell alikemoderate

Cooked together3,400 recipes

Shared aroma: nonanal (fat, citrus).

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

What each ingredient does

Fresh butter: Forms the rich, creamy base that holds the other ingredients together.
Spinach: Adds green color and a mild earthy flavor to the butter.
Herring roes: Provide the main savory flavor and a soft, smooth texture when sieved.
Curly parsley: Adds fresh herbal aroma and bright green flavor.
Capers: Add a sharp, salty acidity that cuts through the richness of the butter.

The step that matters

Pass the herring roes through a fine sieve. Pounding alone leaves fibrous, grainy bits. Sieving breaks down the remaining fibers into a smooth paste, so the butter spreads evenly and feels silky rather than gritty.

Swap the spinach

How well each one fits the dish's main ingredients (butter, roe, parsley, capers, pepper):

Shallotfits better
Chivefits better
Mustardfits about as well
Spinachthe original

Fit is the average pairing score against butter, roe, parsley, capers, 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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Green Butter with Herring Roes