For this you will need a large bowl to sit over a saucepan filled with a couple of inches of barely simmering water, making sure the base of the bowl doesn't touch the water. Break up the chocolate into pieces, add them to the bowl and, keeping the heat at its lowest, leave the chocolate to melt slowly.
The chocolate will take about 10 minutes to melt and become smooth and glossy. (Though the time will vary depending on the amount of chocolate – individual timings are given in each recipe.) Then remove it from the heat, give it a good stir and it's ready for use.
To make chocolate curls: melt the chocolate as above and then pour it on to a flat, smooth surface; the underside of a large plate will do. It should form a circle of about 6 inches (15 cm) diameter and ¼ inch (5 mm) thick. Place the plate in the fridge to chill for 45 minutes. What you want is the chocolate to be set hard enough so that if you press the surface of the chocolate it doesn't leave an indentation.
Now take it from the fridge and use a cheese slicer to make curls (if you don't have one, a sharp knife will do if you hold the blade in both hands). Just pull it all along the chocolate towards you and it should curl up. What is very important to know here is that if it doesn't curl and you end up with a pile of chocolate shavings they'll look just as nice – either way, place them in a rigid plastic container and then put this in the fridge until you need them.