Add the oats, water and ice to a liquidizer or blender. You could also achieve a good result with a stick blender but I would use 1 litre of very cold water rather than ice. Blend for 30 seconds.

Strain the liquid through a nut milk bag, 3 to 4 layers of cheesecloth or even a tea towel folded over a few times. Don’t squeeze the liquid through too much at this stage, that can result in a grainy texture in the final milk.

Then simply bottle and refrigerate, this will last up to 5 days chilled.