Place coffee grounds in the bottom of a French press.
Fill the French press halfway with cool water, and stir. This hydrates the coffee grounds so they don't float on the surface of the water. Add the rest of the water up to the top of the French press, leaving enough room for the lid to sit on top with the mesh filter pulled up.
Stir the coffee and water again and put the lid on the French press with the plunger pulled all the way up. Place in the refrigerator for 12-15 hours.
In the morning, slowly depress the plunger to filter the coffee.
Serve in a 1:1 or 1:2 ratio with milk, water, chocolate milk, hot cocoa, flavored creamer, or any other flavoring you want.
Store any remaining concentrate in jar, bottle, or pitcher in the fridge.