Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a medium bowl, stir together the peanut butter, brown sugar, egg, and protein powder until smooth.
Scoop into tablespoon-sized balls and place on your prepared baking sheet. Flatten slightly with the back of a fork if you like that classic crisscross look.
Bake for 8-10 minutes, just until the edges are set and the tops look slightly crackled.
Let cool on the pan for a few minutes before transferring to a wire rack. Enjoy warm or store in an airtight container for up to a week.