Name: Peanut Butter Cups
Ingredients: 15 pounds white sugar; 4 pints water; 1 large teaspoon cream of tartar; ½ ounce vanilla extract; 5 pounds peanut butter (or 5 pounds roasted peanuts ground to a smooth paste)

Why it works: Sugar and vanilla are a kitchen classic. They rank in the top 8% of all ingredient pairs, and cooks put them together in 35,032 recipes. Both carry beta-damascenone, which smells apple, rose. The science ↓

Peanut Butter Cups

Ingredients

15 pounds white sugar
4 pints water
1 large teaspoon cream of tartar
½ ounce vanilla extract
5 pounds peanut butter (or 5 pounds roasted peanuts ground to a smooth paste)

Directions

Make the sugar base

In a copper kettle, combine sugar, water, and cream of tartar. Stir until sugar dissolves.
Wash down the sides of the kettle and cook the mixture to 335°F (170°C).
Pour the cooked sugar onto a cool slab and fold it as it cools until it is cool enough to handle.

Shape and finish

Add the vanilla extract and pull the mixture over the hook to incorporate air.
Form the mixture into a flat batch on a warm table.
Spread the peanut butter over the flat batch and fold it around to create a round shape.
Pull the mixture into sticks about the thickness of a finger and cut into short pieces.
Leave the pieces on the slab until cold, then pack and use.

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.

Sugar + vanillatop 8% of all pairs

Smell alikelow

Cooked together35,032 recipes

Shared aroma: beta-damascenone (apple, rose).
Sugar + creamtop 9% of all pairs

Smell alikemoderate

Cooked together43,450 recipes

Shared aroma: 2,3-butanedione (butter, sweet).
Vanilla + peanuttop 10% of all pairs

Smell alikestrong

Cooked together1,176 recipes

Shared aroma: guaiacol (smoky, sweet).
Cream + vanillatop 15% of all pairs

Smell alikelow

Cooked together12,301 recipes

Shared aroma: 2-nonanone (fruity, floral).
Cream + peanuttop 21% of all pairs

Smell alikelow

Cooked together490 recipes

Shared aroma: 1-octen-3-one (mushroom, metallic).

Sugar and vanilla barely smell alike, yet cooks put them together in 35,032 recipes: they work on texture and structure more than aroma.

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

What each ingredient does

White sugar: Forms the crystalline candy base that sets firm when cooked and cooled.
Cream of tartar: Acid that helps prevent the sugar from crystallising into a grainy texture.
Peanut butter: Adds fat and peanut flavour, giving the candy a softer, richer bite.

The step that matters

Cooking the sugar to 335°F (170°C). Sugar syrup sets according to its final temperature: too little cooking leaves a soft, sticky candy, while overcooking makes it hard and brittle. Washing down the kettle sides helps prevent stray sugar crystals from triggering graininess.