Add all the ingredients to the mason jar. You may want to crush the coffee crystals a bit with a spoon to help them along.
Screw the lid on tight and shake. It only takes 1-2 minutes of vigorous shaking to get the mix fully combined. Make sure you have all the coffee crystals dissolved, you do not want to see bits on the bottom – see below for an example. Continue to shake if you do see some.
Put the mason jar in the freezer. In about 4-5 hours it will be the consistency of soft-serve ice cream.
Serve in a bowl, ¼ of the mason jar will be one serving.
To enjoy later or the next day, place the mason jar on the counter. Let it thaw at room temperature for about 20-30 minutes. It will then be soft enough to stir and scoop some out.