I’m not sure everyone would agree that it’s permissible to use on Shabbos as it is not “heat brewed” during the process. “
I only brewed my coffee (prior to Shabbos) the same way I would brew it for my morning cup, with boiling water poured through the grounds, but at double the amount of coffee that I would normally use (i.e., 1/4 cup rather than 1/8 cup of ground coffee to every six oz. of water). By making it double strength, it could then be diluted the next day, just like with my tea.