Add milk, vanilla extract, egg yolk and sugar. Use a fork to whisk ingredients until incorporated.
Add flour, baking powder and pinch of salt. Whisk again to combine.
Stir in sprinkles.
Microwave for 90 seconds on 70% or medium-high power. Cool while preparing frosting.
To prepare frosting, use a fork or an electric mixer to beat butter and powdered sugar until creamy. Add in milk, vanilla extract and a pinch of salt. Beat again until combined. Add additional milk if necessary until desired consistency is reached.
Spread or pipe frosting onto cooled mug cake. Add additional sprinkles if desired and enjoy!
Notes
This Recipe Can be Doubled: If you are looking to make 2 servings just double and split the ingredients in mugs, but microwave separately so that the mug cakes are able to cook through equally.
FlavorVariation:If you don't have sprinkles or want vanilla cake, just sprinkles hold the sprinkles to get a white vanilla mug cake. Or you could chocolate chips to get a chocolate chip mug cake.
Alternate cooking method tip: If you have time and are willing to wait, you can also bake this mug cake in the oven for an even fluffier consistently. Just bake at 350 degrees for 15-20 minutes or until a toothpick comes out clean.