Place ground coffee and water in a large pitcher or other container. Stir mixture well until combined; cover pitcher. Let the mixture stand (room temperature) for about 12 hours.

After 12 hours, place a fine wire mesh strainer over a large container. Pour coffee mixture through strainer and into the pitcher. You may need to do this in small batches, discarding grounds and rinsing strainer between batches. TIP: You MAY need to do this an additional time, if you find your strainer isn't "catching" all the fine coffee grounds. 

Rinse out the strainer; line it with a coffee filter. Place the filter-lined strainer directly over the top of a large pitcher. Pour coffee concentrate into the pitcher using the strainer to filter out any remaining coffee grounds. You may also need to do this in batches, as well.

Add vanilla extract; stir well. Cover pitcher (or container); place concentrate in refrigerator (can be stored up to 2 weeks (covered) in refrigerator, if desired.

Fill a glass ¾ full of ice. Pour in coffee concentrate; stir to combine. Add sweetened condensed milk, (enough to sweeten coffee to your liking). Stir well, for best flavor. If necessary, add more coffee concentrate and/or sweetened condensed milk, in order to fill the glass. Stir well. Serve immediately and enjoy!