Step 1

Grind the beans in a coffee grinder on the coarse setting; the ground coffee should resemble coarse sugar or sand.

Step 2

Cut a 6-by-6-inch double thickness of cheesecloth. Put the coffee in the middle and tie tightly with kitchen twine. Put the sachet in a pint Mason jar or other 2-cup glass container. Add the cold water and seal tightly. (If you prefer, you can just add the coffee directly to the cold water and strain through cheesecloth after steeping.)

Step 3

Refrigerate and steep for at least 12 hours, though 18 to 24 hours is best. Remove the sachet, press to extract as much liquid as possible back into the jar and discard the sachet.

Step 4

To serve, pour equal parts cold brew concentrate and cold water over ice. Add milk and sweetener if using.