Step 1

Place ground coffee in a large container. Gradually add 7 cups cold water. Stir gently to be sure all grounds are moistened. Cover with a layer of cheese-cloth. Let stand at room temperature for 15 hours.

Step 2

Remove cheesecloth and use it to line a fine-mesh sieve set over a large pitcher. Pour coffee through sieve into pitcher (do not stir); rinse jar and set aside. Discard cheesecloth with solids.

Step 3

Line same sieve with a large coffee filter and set over reserved jar. Strain coffee through sieve into jar. (It may take up to 45 minutes for all of the coffee to drip through; do not stir or coffee may become cloudy.) Cover and chill. Coffee concentrate can be made 2 weeks ahead. Keep chilled.

Step 4

Fill a glass with ice. Dilute 1 part coffee concentrate with 1 part milk, if desired, or water.