Because this mug cake has a lot of liquid from the berries, it's possible you may have some spatter or overflow in the microwave. To help catch any spatter, place a paper towel on top of the mug when microwaving. Also, be sure to use a mug that is large enough; you will need a microwave-safe mug that holds at least 12 ounces (355 ml). Finally, if you want extra insurance against mess in the microwave, place the mug on top of a microwave-safe plate to catch any potential drips!