Stir continuously until the coffee dissolves. It will take a couple of minutes for the coffee to boil. As soon as it starts to boil, remove it from the heat. Leaving it on the heat any longer will result in the kaimaki disappearing.
Pour 1/2 the coffee into one cup, and then fill your second cup of coffee completely. Return to your first, half-filled cup and fill that one with the remaining coffee. This technique will ensure that each cup ends up with a proper kaimaki. Let sit for about 3-4 minutes, to let the grounds settle, before sipping. (See video here)