Instructions

1. Combine sugar and water in a large heavy saucepan. Stir together over low heat until sugar has mostly dissolved. Raise temperature to high and leave to come to a boil. Use a brush dipped in water to wash down any sugar crystals from the sides of the pot, but do not stir!
2. As soon as syrup starts to turn an amber colour, remove from heat and swirl caramel around in the saucepan. Caramel will continue to cook and become darker in colour even once removed from heat, but if it does not become a rich amber colour, return to heat for 5 more seconds, then remove from heat and swirl to mix.
3. Off the heat, immediately add double cream, whisking at the same time. Caramel will rapidly bubble up, but keep whisking to mix until it has stopped bubbling. Add the butter and salt and mix in until butter has completely melted and is mixed in to caramel.
4. Leave to cool before using, or immediately pour into clean heat proof jars. Store in the fridge. Sauce will keep for up to a month. It will thicken while chilled, so reheat before using.