In a medium bowl, combine the flour, cocoa powder, baking powder and stevia.
Add in the yogurt, milk and vanilla and whisk to combine.
Transfer the batter to a microwave safe dish, (I used a 9cm ramekin lined with parchment paper) and cook in the microwave for 1-2 minutes depending on your microwave. For reference, I used a 700W microwave and it took 2 minutes and 30 seconds. You can also use a toothpick to see when your brownie is done. After the first minutes, insert the toothpick into the center and if it doesn't come out clean with a few crumbs, microwave for another 30 seconds and check again. Repeat until the brownie is done.
Make the frosting as the brownie cools by whisking together the cream cheese, 0 calorie icing sugar and cocoa powder until smooth.
Top the cooled brownie with the frosting, add the sprinkles and enjoy!
Notes
* Stevia - The stevia I use is 2 times as sweet as sugar so you would need half the amount of sugar. If you're using a sweetener that is a 1:1 ratio with sugar, you need to double the amount of sweetener so 2 tbsp instead of 1.