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Dessert

Rock Sugar

A hard candy made by boiling clarified sugar and adding icing, optionally colored.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 8 ingredients
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Why it works: Sugar and egg are a kitchen classic. They rank in the top 21% of all ingredient pairs, and cooks put them together in 122,807 recipes. Both carry 2-nonenal, which smells fatty, green. The science ↓

Rock Sugar

Ingredients

Directions

Prepare the icing

  1. Beat a small quantity of egg white with a fork and gradually add fine powdered sugar until it reaches icing thickness.

Make the rock sugar

  1. Heat ½ pint or 1 pint of clarified sugar in a large sugar pan over medium heat.

  2. Once the sugar has boiled to the correct height, remove it from the heat and quickly stir in a small tablespoon of the icing.

  3. Let the mixture rise twice.

  4. Pour the mixture into a sieve or paper case.

  5. Cover the pan until the mixture sets.

Colour (optional)

  1. For colored rock sugar, stir in carmine for red, powder blue for blue, saffron for yellow, or a mix of saffron and powder blue for green.

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.

  1. Sugar + eggtop 21% of all pairs
    Smell alikemoderate
    Cooked together122,807 recipes

    Shared aroma: 2-nonenal (fatty, green).

  2. Sugar + saffrontop 30% of all pairs
    Smell alikelow
    Cooked together650 recipes

    Shared aroma: 1-penten-3-one (fish, pungent).

  3. Egg + saffrontop 32% of all pairs
    Smell alikelow
    Cooked together535 recipes

    Shared aroma: nonanal (fat, citrus).

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

What each ingredient does

Clarified sugar
Forms the crystalline candy base that sets as the mixture cools.
Egg white
Beaten into the icing to give it body and help the mixture stay light.
Fine powdered sugar
Sweetens and thickens the egg white into an icing with a stable structure.

The step that matters

Removing the sugar at the correct boiling height. Sugar must reach the right temperature before it is removed from the heat. Too little cooking leaves the candy soft and sticky, while overcooking makes it hard and brittle and it may crystallize poorly.

Swap the saffron

The recipe marks saffron as optional. How well each one fits the dish's main ingredients (sugar, egg):

  1. Cinnamonfits better
  2. Nutmegfits better
  3. Gingerfits better
  4. Saffronthe original

Fit is the average pairing score against sugar, egg. 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.

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