You can use any type of mug for the cake. A larger deeper mug will create a softer moister cake, while a smaller shallower mug will create a firmer cake. Soften a stick of butter on the countertop and scoop a tablespoon into the mug. You can use salted or unsalted butter, or margarine. Adding the chocolate chips will create a chocolate flavored mug cake. If you prefer a vanilla cake, you can add an additional tablespoon of vanilla extract instead. Put the mug in the microwave for 50 seconds on full power. After 50 seconds, check to see if the cake is baked by sticking a toothpick straight down into the center. The toothpick should come out clean. If there is gooey cake residue on the toothpick, put the mug back in the microwave and cook it in 30 second increments until done.  Take care not to overcook. If you microwave the cake for too long, it will dry out. It shouldn't need to be cooked for any longer than 2 minutes. Don’t worry about the toothpick creating a hole in the cake, you won't be able to see that when you frost it later. Microwaves often don’t distribute heat as evenly as ovens do. Let the cake sit on the counter for 1-2 minutes after baking, giving time for the heat to distribute throughout the mug. Take a spoon and dig in. If you'd like, frost and decorate the cake first. Be careful when removing the mug from the microwave. Use a hot pot holder or a towel to lift it out. It will probably be too hot to grab.

TL;DR in Chinese:
挑选马克杯。 添加黄油。 加一两汤匙巧克力屑（可选）。 烤马克杯蛋糕。 静置一会儿。 好好享用蛋糕！用汤匙挖着吃。