In a microwave-safe mug add butter and microwave for 15 seconds or until the butter is melted
Then add the sugar, vailla, eggs, milk, flour, baking powder and mix well
Add in the sprinkles and just mix through
Microwave for 1-1 and half minutes ( time needed will depend on each microwave) Check if it is cooked by inserting a skewer inside and if it comes clean, then its cooked.
Cool down, if you wish to add icing on the top, then use my vanilla buttercream recipe and add colouring.