Melt 1 cup dark chocolate with butter in 30 second intervals until melted fully
Whisk eggs,, sweeteners, greek yogurt, and vanilla together, then put chocolate mixture in as well
Whisk protein powder, flour, and cocoa powder together, then add into wet mixture
Fold in chocolate chips, saving some for topping
Pour into 8x8 pan lined with parchment paper and bake at 350 for 23 minutes
Let cool completely
Dampen a knife with cool water for smoother slicing