Why it works: Mustard and pepper are a kitchen classic. They rank in the top 9% of all ingredient pairs, and cooks put them together in 15,430 recipes. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓
Cheese Toast
Ingredients
Directions
Make the cheese sauce
In a double boiler, combine cheese and milk.
Stir until the cheese is blended with the milk.
Add beaten egg yolks, mustard, salt, and red pepper.
Serve
Cook lightly and serve immediately on toast.
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.
Photo for illustrative purposes only · Contact us to use it
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.
-
Mustard + peppertop 9% of all pairsSmell alikemoderateCooked together15,430 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
-
Cheese + milktop 10% of all pairsSmell alikemoderateCooked together4,426 recipes
Shared aroma: delta-dodecalactone (sweet, creamy).
-
Cheese + mustardtop 11% of all pairsSmell alikemoderateCooked together1,805 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
-
Cheese + peppertop 18% of all pairsSmell alikemoderateCooked together7,861 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
-
Milk + eggtop 18% of all pairsSmell alikemoderateCooked together88,785 recipes
Shared aroma: 2-nonenal (fatty, green).
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
What each ingredient does
- Cheese
- Melts into the milk to form the smooth, rich body of the sauce.
- Egg yolks
- Emulsify and thicken the cheese mixture into a creamy, spreadable sauce as they gently cook.
- Milk
- Provides the liquid that melts the cheese and keeps the sauce smooth and moist.
- Mustard
- Adds sharp flavor that balances the richness of the cheese and egg yolks.
The step that matters
Add the egg yolks to the warm mixture. Egg yolks thicken when heated gently but can scramble if the sauce is too hot. Keep the heat low in the double boiler and stir steadily so the sauce becomes smooth rather than grainy.
Swap the mustard
How well each one fits the dish's main ingredients (cheese, milk, egg, pepper):
- Capsicumfits better
- Potatofits better
- Asparagusfits better
- Mustardthe original
Fit is the average pairing score against cheese, milk, egg, 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.
More cheese toast recipes
You might also like
The free Flavor Lab newsletter: one surprising pairing a week and the molecular reason it works, in 60 seconds. No spam, unsubscribe anytime.
Prefer an account? Create a free account to save pairings and unlock the full chemistry.

Macaroni and Cheese102 recipes
Cheese Making50 recipes
Cheese Fritters34 recipes
Cheese Omelette31 recipes