Buying a sugar thermometer seems like the sort of thing only crazy people do. It seems to sit along deep fat fryers and foam-generating siphons as the sort of equipment only professionals and obsessives really need.

The crucial thing about a sugar thermometer is that it allows you to measure a very simple property – the concentration of sugar in a syrup. That’s it.

Water  boils at 100°C (at sea level), and adding sugar to the water raises the boiling point up and up. Caramel is just very hot sugar, that has started to develop complex flavours, a little like browning meat. So a sugar thermometer makes caramel as well as jam a much more predictable affair, and removes much of the guesswork. I have both a glass thermometer, and a new and shiny digital thermopen. If using a glass one, be careful that you have enough liquid to immerse to the line it indicates, or the temperature won’t be accurate. You also need to make sure you put the thermometer in the pan early on – adding a cold thermometer to boiling caramel is a recipe for broken glass in your caramel. A good idea would be to warm the thermometer in the cream, then put into the caramel mixture once the cream is mixed in.

I like making caramel, because the ingredients are so simple and cheap: sugar, butter, cream – but the results are so complex in flavour. Depending on how long you cook this, and to what temperature, you can have a caramel sauce, soft, chewy caramels or hard toffee. I prefer a fairly soft caramel, that is still firm enough to slice and wrap.

These chocolate caramels are a beautiful combination of the buttery flavour of caramel with dark chocolate to balance the sweetness. I was surprised that the recipe asks you to cook the caramel with the chocolate in to a high temperature – I expected the chocolate to burn. I stirred fairly frequently to make sure it didn’t catch on the bottom of the pan, and there was no trace of burnt flavour in the caramel, so I guess it worked.

For more on regular caramels (without the chocolate), Dan Lepard has a great all-purpose caramel recipe he wrote for the Guardian a while back.

Salted chocolate caramels

Adapted from Smitten Kitchen, who in turn, adapted from Gourmet

Usually I would list the ingredients as I go, but it’s especially important to have everything prepared in advance for caramel making, so I have separated the preparation and cooking stages.

Preparation:

Line an 8 inch square pan with foil or two strips of baking parchment at right angles. If using foil, brush with a thin coating of vegetable oil. Set aside.

Chop:

150g dark chocolate

into small pieces and put into a heatproof bowl.

Place

240ml double cream

into a small pan.

200g granulated sugar

Put into a thick-bottomed pan, something quite tall as it will bubble up later (use your best pan for the sugar, and second best for the cream)

Measure out:

60g golden syrup

and

30g butter

and

1/2 tsp coarse sea salt, crushed into fairly small crystals

(this is optional, but very good. Maldon salt or fleur de sel is good. Table salt is not – it will be far too salty).

and put aside, near the stove.

Cooking:

Heat the cream until tiny bubbles start to form at the edge of the pan

Pour immediately over the chocolate, and stir gently until the chocolate is completely melted and the whole thing is smooth.

Add a tablespoon of water to the sugar in the pan, just enough to make it a little damp, and put over medium heat until the sugar dissolves. Keeping a lid on will help it heat faster, and make sure that the sugar gets dissolved properly. Once it is all clear and liquid, remove the lid, turn the heat up to high and boil furiously to make caramel. You want to bring it to a fairly dark amber, without burning it. When it starts to become golden, turn the heat down a little so you can control the process a little better.

Remove from the heat and add the golden syrup, and then, gradually,  the chocolate and cream ganache. Stir after each addition. It will bubble up furiously as the water in the cream is liberated to steam all at once – the caramel will be much hotter than the boiling point of water.

Once everything is combined, return to the heat with a sugar thermometer and bring to the boil again. Heat until the temperature reaches 255F/124C. Any lower, and you risk a pourable, liquid caramel (although if you want caramel sauce, that’s fine). You can take it higher, and get a firmer caramel, until it starts to become toffee.

Immediately remove from the heat, stir in the butter and the salt if using. Stir to incorporate the butter thoroughly, then pour into the prepared tin, and leave to cool and set.

Once completely cold, lift the caramel out of the pan with the paper or foil, and turn upside-down onto a cutting board. Use a large knife to slice into strips and then squares. Wrap each piece in a square of baking parchment or greaseproof paper. Or just eat quickly 🙂

Store in a sealed container – exposure to the air will allow the caramel to absorb water from the air, and it will start to become too sticky.