In a saucepan combine the sugar, milk and cream, put it on a high heat and keep stirring until bubbes form at the edge. Turn down the heat. Meanwhile whick the eggs in a bowl. Add half the cream mixture to the eggs, stir well, then add the eggs to the rest of the cream in hte saucepan and, over a medium heat, stir constantly until the mixture coats the back of a metal spoon. Add anything else you want at this point, excluding nuts and chocolate chunks. Let the mixture cool in the fridge for a few hours then pour into an ice-cream maker. Now add chocolate chips or nuts and follow the ice-cream maker's instructions.
To make a chocolate-based ice cream adding 110g cocoa powder to the milk and cream mixture at the beginning.