I first saw the recipe on Pinterest. I will have to look for the link again. Oddly enough, this process was just on the Pioneer Woman's cooking show this past Saturday. Slightly different than how I did it but I am sure it is just as good.
Here's what you need for the coffee concentrate:
1 Pound Ground Coffee of your Choice (I used Starbucks Dark Espresso Roast)
1 gallon water
1 large Bowl
Coffee Filters or cheese cloth
1) Dump the pound of ground coffee into the large bowl.
3) Cover and let sit 12-24 hours
It sounds like a long process but it really isn't. The straining only took me about 20-30 minutes. It made approx 3/4 of a gallon. It will last a month in your refrigerator.