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

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 the ingredients

Set the butter in ice to chill.
Boil the spinach until tender, then pass it through a sieve to save the pulp. Dust the spinach pulp with pepper.
Remove the oil from the herring roes, then pound them in a mortar and pass through a fine sieve.
Finely mince the parsley to yield at least 1 tablespoon.
Mince the capers finely.

Combine and serve

Mix all ingredients together with a wooden spoon and shape as desired. 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).
Pepper + parsleytop 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

Butter: Provides fat and richness, giving the green butter its smooth, spreadable body.
Herring roe: Adds savoury, rich flavour and a soft, creamy texture once pounded and sieved.
Spinach: Supplies the green colour and a mild, earthy flavour through its pulp.
Capers: Add a sharp, acidic bite that cuts through the richness of the butter.

The step that matters

Pass the spinach and herring roe through a fine sieve. Sieving breaks down fibres and lumps so the butter becomes smooth rather than grainy or stringy. Thorough pulping also keeps the colour even and the texture silky when the butter is shaped.

Swap the spinach

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

Shallotfits better
Chivefits better
Mustardfits about as well
Spinachthe original

Fit is the average pairing score against butter, pepper, roe, parsley, capers. 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