Put the sugar and the cornflour (or custard powder) in a small bowl and add 3 or 4 tablespoons of milk from the pint. Mix together well until you have a smooth paste. (If making chocolate custard, add a spoonful or 2 of cocoa powder at this stage).

Heat the remaining milk in a saucepan until just before boiling (there will be small bubbles around the edge of the pan). Turn the heat down.

Using a whisk, drizzle the paste into the hot milk, whisking constantly. The custard will start to thicken the longer you leave it.

Add the vanilla (or other liquid flavouring) and stir in. Do a taste test for sweetness and flavour and adjust if necessary. If your mix is too runny, make a bit more paste and add in, if it thickens too much, add a bit more milk.

Remove from the heat and serve.

Enjoy!