Line a 6-inch square baking dish with parchment paper and set it aside.
In a large bowl, combine crispy rice cereal with protein powder and stir well, until evenly combined.
Cut the chocolate into small chunks, then place in a microwavable bowl and microwave for 30 second intervals, removing and stirring at each 30 second interval, until the chocolate has melted. Make sure that you stir often so that the chocolate does not burn. As an alternative, you can melt the chocolate using the bain marie method.
Pour melted chocolate in the protein rice mixture and stir until the cereal is evenly coated with melted chocolate.
Transfer the mixture to your prepared baking dish. Press gently with your fingertips just until completely spread out, then refrigerate for at least one hour before cutting into squares.