Name: Chocolate Walnut Slice
Ingredients: 10 lbs scrap (taffy, caramels, etc.); 2 quarts water; 1 quart cream; cocoa to flavor and color; a little vanilla; 1 to 1½ lbs English walnut pieces

Why it works: Cocoa and vanilla work together. They rank in the top 4% of all ingredient pairs, and cooks put them together in 357 recipes. Both carry sotolon, which smells curry, maple. The science ↓

Chocolate Walnut Slice

Ingredients

Directions

Make the base

Combine 10 lbs of scrap and 2 quarts of water in a kettle.
Heat and stir until dissolved.
Strain the mixture.
Return it to the heat.
Cook until it reaches 240°F (soft ball stage), stirring constantly.
Add 1 quart of cream.
Continue cooking until it reaches 256°F or 258°F (good crack stage).
Remove from heat.
Add cocoa and vanilla to taste.

Shape and slice

Pour the mixture onto a greased slab.
Sprinkle with walnut pieces.
Fold in the edges.
Knead until stiff.
Form into a roll about 3 inches thick.
Roll until almost cold.
Using a sharp knife, cut into slices ½ inch thick.
Wrap in wax paper.

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.

Cocoa + vanillatop 4% of all pairs

Smell alikemoderate

Cooked together357 recipes

Shared aroma: sotolon (curry, maple).
Vanilla + walnuttop 10% of all pairs

Smell alikestrong

Cooked together2,730 recipes

Shared aroma: eucalyptol (eucalyptus, herbal).
Cream + vanillatop 15% of all pairs

Smell alikelow

Cooked together12,301 recipes

Shared aroma: 2-nonanone (fruity, floral).
Cocoa + walnuttop 17% of all pairs

Smell alikemoderate

Cooked together29 recipes

Shared aroma: sotolon (curry, maple).
Cream + walnuttop 21% of all pairs

Smell alikelow

Cooked together1,982 recipes

Shared aroma: octanal (fat, soap).

Cream and vanilla barely smell alike, yet cooks put them together in 12,301 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

Scrap candy (taffy, caramels): Provides the sugar base that melts and sets into the body of the slice.
Cream: Adds fat and richness, softening the texture of the candy.
Cocoa: Supplies chocolate flavor and the brown color of the slice.
English walnut pieces: Add crunch and a nutty flavor that contrasts with the smooth candy.

The step that matters

Cooking to 256°F or 258°F after adding the cream. Sugar concentration determines firmness once cooled. Stopping short leaves the slice soft and sticky, while overcooking makes it hard and brittle. Cooking continuously with stirring prevents scorching on the bottom of the kettle.