In a large jug, mix together Ground Coffee (2 cup) and Cold Water (3 1/2 cup). Cover with plastic wrap and let sit at room temperature for 12 hours.
Place a paper coffee strainer in a regular metal strainer, and gently pour the coffee water through both into a large bowl or jug. You don't want any bits getting through, so pour the coffee a little at a time. You will end up with about 2 cups of coffee concentrate.
Serve in a glass half filled with the concentrate, half filled with either Milk (to taste) or Water (to taste) to dilute.