1. To microwave, break 115 g/4 oz plain chocolate into squares or chop it into small pieces. Place in a heatproof bowl and cook on medium (50% power) for 2 minutes. Milk and white chocolate should be melted for the same time, but on low (30% power).
2. To melt chocolate over hot water, bring a small saucepan of water to the boil. Turn off the heat and place the bowl of chocolate over the hot water. The bowl must not touch the water nor should any drops of water be allowed to fall into the chocolate or it will become grainy.
3. Leave the chocolate until very soft then stir it lightly.