Pop the filtered water and ground coffee into an air tight container.
Stir the mixture a few times and after 2 minutes all the coffee should be floating on the top, stir for another minute and then leave in the fridge, coolbox or somewhere cool for 12-16 hours.
Filter twice through the aeropress, cafetiere or other coffee filter.
Drink neat or if it's too strong for your taste dilute with more filtered water. Enjoy it black for a caffeine kick, with cold milk as a frappe, or even add a shot to your morning smoothie!