Name: Fried Onions with Parmesan Cheese
Ingredients: 6 large mild onions; ½ cup cream; ¼ teaspoon pepper; ¼ teaspoon salt; 3 eggs; ¼ pound Parmesan cheese, grated; boiling lard for frying; melted butter with a little mustard for serving

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 ↓

Fried Onions with Parmesan Cheese

Ingredients

Directions

Peel and slice the onions into ½-inch thick rounds.
In a bowl, mix flour, cream, pepper, salt, and eggs; beat for 10 minutes.
Stir in the grated Parmesan cheese and then add the onions.
Heat the lard until boiling.
Using a fork, dip each onion slice into the batter and fry gently until golden brown.
Drain the fried onions and arrange them on a serving plate.
Serve with melted butter mixed with a little mustard in a sauceboat.

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.

Onion + mustardtop 6% of all pairs

Smell alikestrong

Cooked together9,259 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Cream + buttertop 8% of all pairs

Smell alikemoderate

Cooked together41,516 recipes

Shared aroma: delta-dodecalactone (sweet, creamy).
Parmesan cheese + buttertop 9% of all pairs

Smell alikemoderate

Cooked together4,163 recipes

Shared aroma: guaiacol (smoky, sweet).
Pepper + mustardtop 9% of all pairs

Smell alikemoderate

Cooked together15,430 recipes

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

Swap the mustard

How well each one fits the dish's main ingredients (onion, cream, pepper, egg, parmesan cheese, butter):

Potatofits better
Spinachfits better
Asparagusfits better
Mustardthe original

Fit is the average pairing score against onion, cream, pepper, egg, parmesan cheese, butter. Candidates are from the same food group and used in at least 100 recipes.