Place the cream and sugar (if using) in a small pot. Heat up the cream over medium heat until it steams. Stir constantly to dissolve the sugar. If by mistake it breaks into a bowl, then you need to cool it down a bit before using it.
Melt the chocolate in a bowl. You can do it in the microwave in intervals of 30 seconds, mixing in between each interval. Alternatively, you can melt it in a bain-marie over low heat. Make sure that the bottom of the bowl doesn't touch the surface of the water.
Remove the chocolate from the bain-marie if using. Add all the cream onto the chocolate.
With a spatula, make small circles at the centre of the bowl. You'll see that it will start to come together at the centre on its own and then expand towards the sides.
When everything looks evenly dark, scrape down the sides of the bowl and keep mixing until everything looks incorporated and shiny.
Let it cool down until it has a thicker texture, like a fudge or dulce de leche. Give it a mix every once in a while so it cools evenly. When it's ready it should be at room temperature. If it's cold it will take 20-30 minutes to cool down and if it's hot it could take up to an hour.