To tell if your custard is ready, coat your wooden spoon with custard and dab it with a fingertip. If it leaves a mark, your custard is ready; otherwise carry on heating and stirring. You need to cook the egg yolks without boiling them. Custard should be cooked between 69°C and 85°C. Cook at a higher temperature for a thicker mixture.
To make your custard last longer, pour it into a small bowl and plunge into a bath of iced water, continuing to stir it until completely cool. Your custard will be creamier if you refrigerate it 24 hours before serving. If you cover it with cling film to keep the air out, custard will keep for up to three days in the fridge. For creamier custard, simply add a dollop of cream.
Custard is often served with tarts and puddings like treacle sponge, but you can also flavour it according to your recipe. For a naughty but nice pud, try chocolate custard with your chocolate cake (you might as well go the whole hog!), or mint custard with peppermint tart.