Starbucks Brown Sugar Syrup

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Two ingredients, one failure mode: the syrup turns to a solid block of sugar crystals in the fridge after a few days.

It happens because the syrup was boiled. Boiling drives off water and pushes the sugar concentration past what the remaining water can hold, so it comes back out of solution as crystals as soon as it cools.

Heat it only until the sugar has dissolved. That is somewhere around 80°C and it takes about five minutes. There is no reason to go further.

The other cause of crystals

Sugar crystals stuck to the side of the pan. One crystal falling back into the syrup acts as a seed, and crystallisation spreads from it through the whole batch.

Do not stir once it is warm, and if you see crystals on the side, brush them down with a wet pastry brush.

Swirl the pan instead of stirring. It is enough to move the sugar around.

A spoonful of corn syrup stops it entirely

If you want a syrup that keeps for a month with no risk, add a tablespoon of golden syrup or corn syrup.

These are invert syrups — their sugar molecules are different shapes, and mixed in among the sucrose they physically get in the way of crystals forming. It is the same reason it is used in sweet-making.

Not essential. Very effective.

Dark brown sugar

Dark brown rather than light. The molasses content is what gives the syrup its depth and its colour, and light brown sugar produces something noticeably paler and flatter.

Muscovado gives an even stronger, more treacly result, which is good but starts to dominate a coffee.

What you need

• 200 g dark brown sugar
• 200 ml water
• 1 tbsp golden syrup (optional, for keeping)
• 1/2 tsp vanilla extract
• a pinch of salt

Method

1. 1. Sugar and water into a small pan. Stir now, while it is cold, until the sugar is wet through.
2. 2. Medium-low heat. Bring it to a bare simmer and no further.
3. 3. Swirl the pan occasionally. Do not stir.
4. 4. When the sugar has fully dissolved — about 5 minutes, and the syrup will look clear rather than cloudy — take it off.
5. 5. Stir in the golden syrup, vanilla and salt.
6. 6. Cool completely, then bottle.

The pinch of salt

A quarter teaspoon in a batch this size. It sharpens the perception of sweetness and suppresses any bitter edge from the molasses, and it is the difference between a syrup that tastes of sugar and one that tastes of brown sugar.

Using it

Iced shaken espresso: 2–3 tablespoons, two shots of espresso, ice, shaken, then oat milk.

Latte: 2 tablespoons in the cup before the coffee.

Cold brew: 1–2 tablespoons, stirred, since there is no shaking to disperse it.

Start lower than you think. It is sweeter than it looks.

Storing

A month in the fridge in a sealed bottle, or two weeks without the golden syrup.

If it does crystallise, it is recoverable: add a splash of water and warm it gently until the crystals dissolve, then cool it again without stirring.

Discard it if it smells fermented or you see anything cloudy suspended in it.