Add all the ingredients to a blender (minus sprinkles) and blend until smooth.
Fold in the sprinkles.
Grease two microwave safe mugs or ramekins and divide the batter between the two. Depending on the size of your ramekins, you might make three cakes!
Microwave on high for 2 minutes. Remove and top with whipped cream/yogurt and enjoy!
Notes
If you don't have a microwave, you can bake the cakes at 350ºF for 20 - 25 minutes.
Plant-based protein powder absorbs more liquid than a whey based protein, so the recipe will not be the same if you don't use plant-based. I have not tested with whey or collagen, so can't say exactly what the measurements would be!
To store: Mug cakes don't typically store well, but if you do have leftovers, they can be stored in an airtight container in the fridge for up to 2 days. Just pop them back into the microwave for a few seconds before serving to warm them up.