Name: Butter-Scotch
Ingredients: 1 lb best cane sugar; ½ cup milk or cream; ½ cup water; a pinch of cream of tartar; 3 oz butter; flavouring

Why it works: Milk and butter are a kitchen classic. They rank in the top 7% of all ingredient pairs, and cooks put them together in 81,283 recipes. Both carry (z)-4-heptenal, which smells biscuit, cream. The science ↓

Butter-Scotch

Ingredients

Directions

Make the toffee

Dissolve the sugar slowly in the milk and water.
Add the cream of tartar.
When warm, add the butter a little at a time.
Boil carefully to 280°F (138°C).
Add the flavouring and pour onto an oiled tin.

Cut and wrap

When half set, mark into squares.
Once completely cold, separate the pieces and wrap each in wax paper, then in tin foil.

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.

Milk + buttertop 7% of all pairs

Smell alikemoderate

Cooked together81,283 recipes

Shared aroma: (z)-4-heptenal (biscuit, cream).
Cream + buttertop 8% of all pairs

Smell alikemoderate

Cooked together41,516 recipes

Shared aroma: delta-dodecalactone (sweet, creamy).
Sugar + creamtop 9% of all pairs

Smell alikemoderate

Cooked together43,450 recipes

Shared aroma: 2,3-butanedione (butter, sweet).
Sugar + buttertop 17% of all pairs

Smell alikemoderate

Cooked together98,233 recipes

Shared aroma: guaiacol (smoky, sweet).
Milk + creamtop 18% of all pairs

Smell alikemoderate

Cooked together29,399 recipes

Shared aroma: delta-dodecalactone (sweet, creamy).

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

What each ingredient does

Best cane sugar: Forms the sweet crystalline base that sets into the brittle toffee texture.
Milk or cream: Adds fat and milk solids that give the butterscotch its creamy, rounded flavour.
Butter: Adds richness and fat, softening the set toffee and contributing to its flavour.
Cream of tartar: Acidifies the syrup, helping prevent sugar from crystallising unevenly.

The step that matters

Boil carefully to 280°F (138°C). Sugar syrup hardens as its temperature rises, so stopping short leaves a soft, sticky toffee while overcooking makes it bitter or brittle. Boiling gently and watching the thermometer keeps the set firm but not burnt.

“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.