Name: Toffee, Treacle
Ingredients: 2 cups treacle; 2 oz. brown sugar; 1 oz. butter; ½ cup vinegar; 1 teaspoon bi-carbonate of soda; essence of almonds to taste

Why it works: Butter and almond are a kitchen classic. They rank in the top 11% of all ingredient pairs, and cooks put them together in 9,245 recipes. Both carry 2,3-pentanedione, which smells butter, sweet. The science ↓

Toffee, Treacle

Ingredients

Directions

Make the toffee

In a sugar boiler or stewpan, combine the brown sugar and vinegar, and heat until dissolved.
Add the treacle and boil until it reaches 247°F (large ball stage).
Remove from heat, then add the bicarbonate of soda dissolved in a little hot water, butter, and almond essence.
Boil again until it reaches 290°F (small crack stage).

Set and break

Pour into an oiled or greased tin.
When partially set, mark into bars or squares, and once firm, break into sections.

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.

Butter + almondtop 11% of all pairs

Smell alikemoderate

Cooked together9,245 recipes

Shared aroma: 2,3-pentanedione (butter, sweet).
Sugar + vinegartop 15% of all pairs

Smell alikemoderate

Cooked together20,806 recipes

Shared aroma: beta-damascenone (apple, rose).
Sugar + buttertop 17% of all pairs

Smell alikemoderate

Cooked together98,233 recipes

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

Smell alikemoderate

Cooked together15,679 recipes

Shared aroma: 1-penten-3-one (fish, pungent).
Butter + vinegartop 23% of all pairs

Smell alikemoderate

Cooked together13,513 recipes

Shared aroma: isoamyl acetate (banana, pear).

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

What each ingredient does

Treacle: Provides the dark colour, rich flavour and chewy body of the toffee.
Brown sugar: Adds sweetness and caramel flavour while dissolving into the syrup.
Vinegar: Adds acidity that helps prevent crystallisation, keeping the toffee smooth.
Bicarbonate of soda: Reacts with the acid and adds gas bubbles, lightening the toffee's texture.
Butter: Adds fat for a softer bite and a rounder, richer mouthfeel.

The step that matters

Boil again until it reaches 290°F (small crack stage). Sugar syrup concentration determines hardness once cooled. Stopping early leaves the toffee soft and sticky, while overheating makes it brittle or burnt. Adding the bicarbonate causes foaming, so the pan should be large enough.