Put everything into a saucepan and bring to the boil. If everyone wants sweet tea, add the sugar too - about four or five teaspoons. This is the traditional way of doing it, but you could leave the sugar out and let everyone sugar their own tea if they want. Watch the pan carefully and when it boils, lift the pan off the heat quickly to stop it boiling over, turn the heat down a little and replace the pan. Lift it off again as soon as it starts frothing. Do this two or three times more and the tea is ready to serve. Use a tea strainer to catch the bits of ginger and tea-leaves.