Mix all ingredients together in a mug/small bowl until it has the consistency of cake batter - add a splash of milk if it's looking too dry
Microwave for 50 seconds, or until the cake has risen and cooked through - test with a skewer or fork and make sure it comes out clean
If still not cooked, microwave in 10-second bursts until you get your desired result
*If you add the apple, please bear in mind that you will have to adjust the cooking time accordingly. Just microwave the cake in extra 10-second bursts until the cake has risen and cooked through - test with a skewer or fork and make sure it comes out clean.You can also make this in the oven instead of the microwave. Just bake at 180 degrees Celsius (350 degrees Fahrenheit) for around 15 minutes, or until risen and an inserted skewer or fork comes out clean.Adapted from Kirbie's Cravings.