Make the coffee concentrate: Combine cold water and coffee grounds in a container. Stir to moisten all the grounds. Cover with plastic wrap and leave at room temperature to steep for 12-24 hours. Place a coffee filter into a wire strainer and strain, discarding grounds. Transfer coffee concentrate to a glass jar and refrigerate. It will keep for several weeks in the fridge (but it won't last that long ;)
To make an iced coffee: In a large glass, combine coffee concentrate, water, sugar, half and half and milk. Stir well. Add ice cubes and enjoy!
You can play around with the proportions of coffee concentrate to water, to taste. The 1/2 cup of water makes an iced coffee a little stronger but mellows out nicely as the ice melts. If you prefer it a little lighter, add the 2/3 cup of water or more from the start. The same goes for the added cream and milk. You can use as much or as little of both or either as you like, to your taste.
Note: *Instant dissolving sugar is available in the sugar section of most grocery stores or at most Bulk Barns and is a special sugar that is made to dissolve easily in cold liquids.
Note that regular sugar will not dissolve in cold liquids, so can't be substituted as is. All is not lost though. Just make a simple syrup by bringing 1 cup water to a boil and adding 1 cup sugar and stirring until completely dissolved. Remove from heat, let cool and then store in a jar to add to your coffee as needed. (Can double or triple this recipe)