In a pan, sprinkle the sugar evenly on the bottom.
On medium heat, start heating the sugar to melt it. Use a spatula to make sure the sugar is melting evenly. The sugar will start to clump up, but keep moving it around as the clumps start to melt.
The sugar will start to caramelize and colour. Keep a close eye on it at this point as it may burn quickly.
Mix the caramel to make sure it heats evenly, and cook it till the caramel turns a very dark amber colour.
Leave the caramel for just a few seconds longer till it just starts to smell like it's burning and immediately add half the butter (4 tbsp/ 55g), and whisk it in until it is well incorporated (about 1-2 minutes).Since the caramel is very hot, adding the butter may cause it to splatter, so be careful!
Add the salt and cream and mix them in until you get a smooth mixture.
Turn off the heat and add the chocolate and let it melt in the residual heat. Whisk it until it is nice and smooth (if the mix is grainy add just a tablespoon more of cream to make the chocolate smooth).
Transfer the chocolate into a bowl and let it chill in the fridge for about an hour till it is cold but not hard.
Once the mix has completely cooled, it should be thick like a ganache.
Add the rest of the butter into the chocolate mix and with a hand beater, beat the mix until the butter is fully incorporated and the chocolate ganache is whipped and lighter in colour.
Transfer the mix into a piping bag with a small star tip and fill the Paris Brest pastry.
Caramel Drizzle
Sprinkle 1/2 cup of sugar evenly on the bottom of a pan and heat the sugar until it starts to caramelize.
Mix and move the sugar around the pan to make sure it caramelizes evenly.
When the sugar turns light amber in colour, immediately remove from the heat.
Using a spoon or a small whisk, drizzle the caramel over the top of the Paris Brest. Take care to not spill the caramel on your hand/skin as it will be very very hot!