Set up a bain-marie, or double boiler so you can heat the coconut butter slowly without burning it. I do this by filling a small saucepan about halfway with water and then placing a pyrex bowl on top of it.
Simmer the water and then add all the ingredients to the top bowl and warm up slowly. Use a whisk to blend the mixture.
Whisk for a few minutes, or until the mixture is getting a bit thick. It will thicken a bit more when it cools so it's OK if it's a bit fluid when warm.
Take the bowl off the heat and cool at room temperature. You can also cool it faster if you place it the refrigerator for a few minutes.
Use the icing to frost cookies, muffins, and cupcakes. Store covered in the refrigerator for a week or so.