Line a standard loaf tin (23cm by 13cm) with greaseproof paper, then use a flavourless oil to grease the greaseproof paper. This will make removing the caramel easier when it has set.
Add the caster sugar to a heavy bottomed pan and heat the sugar until it starts to turn golden.
Whilst the sugar is cooking bring the cream to a boil in another pan, don't be tempted to skip this step as it will cool your caramel down too much and cause it to crystallise.
When the caramel has reached the correct colour and all the sugar has dissolved, remove the sugar from the heat and add half the warm cream.
The caramel will bubble up and a lot of steam will come out, keep your hands out of the way as the escaping steam will be hot.
When the bubbles subside, add the rest of the cream and again when it has finished bubbling add the butter and Cointreau and stir.
Return the pan to the heat and cook the caramel until it reaches 123-124C, then pour the caramel into the pan and leave to set for at least 4 hours.
When the caramel has set, turn it out from the pan, cut the caramel into portions with a sharp knife or a cutter, whichever shape you like.
Place the caramels on a sheet of greaseproof paper or a silicone mat, you will return them to this sheet when they're dipped.
Take the chocolate and put 250g in a bowl and melt it over a bain-marie until it reaches 45C, not all of the chocolate may have melted but don't let it get too hot or you will have to add too much chocolate to cool it down.
Gradually add the rest of the chocolate until it cools to 32C, if you need to, place the tempered chocolate into a smaller bowl so that it makes dipping the caramels easier.
Using a dipping fork, drop the caramels into the chocolate and coat them in chocolate, use the fork to retrieve the caramel and remove the excess by gently tapping the fork against the side of the bowl.
Gently slide the truffle on to the paper or mat and wipe the fork again before dipping more caramels.
You'll need to work quickly as the tempered chocolate will set really fast. Any excess chocolate can be poured into any silicone moulds you have and left to set before being used again to temper more chocolate where necessary.