Use a fork to stir together all ingredients except the chocolate chips in a 10 to 12 ounce microwave-safe mug.
Microwave on high until the cake is cooked, about 1 minute 30 seconds. Pause cooking once halfway through and open the microwave door to prevent the cake from overflowing.TIP: Depending on the wattage of your microwave, you may need another 15 seconds.
If desired, sprinkle the chocolate chips on top. Serve while still warm.
For a gift in a jar:
Whisk all the dry ingredients together and place in a 32-oz wide mouth mason jar. Pack down the cake into the jar to make room for the chocolate chips.
Place chocolate chips into a plastic sandwich bag or cellophane bag (not zipper sandwich, won't fold and fit nicely in top of jar). Add a twist tie to close the bag. Nestle the bag of chocolate chips on top of the cake mix and place lid on jar.
Add label to outside of jar or tie a jar tag around the rim of the jar. (Get the free printable in the post)
To make a mug from the jar:
Measure out 1/2 cup of tightly packed cake mix from jar and add to mug.
Stir in 4 tablespoons milk, 2 tablespoons oil, and 1/2 teaspoon vanilla.
Microwave on high until the cake is cooked, about 1 minute 30 seconds. Pause cooking once halfway through and open the microwave door to prevent the cake from overflowing.
If desired, sprinkle 1 tablespoon chocolate chips on top. Serve while still warm.
Notes
Add a pinch of instant espresso powder for deeper flavor if you have it on hand.
Instead of using regular dairy milk, you can use unsweetened almond milk as a non-dairy option. Other nut milks will likely work as well.