Preheat the oven to 350ºF. Use a non-stick baking sheet or line a baking sheet with parchment paper. Set aside.
In a mixing bowl, beat together the peanut butter, sugar, and egg using an electric mixer, until well combined.
Scoop about 1 tbsp of the dough and roll it into a ball. Place on the prepared baking sheet. You may need to grease your hands if the dough is too sticky. Repeat with the remaining dough.
Flatten each peanut butter ball with a fork, making a criss-cross decoration.
Bake in the preheated oven for about 10 minutes or until the edges are just slightly golden. Remove from the oven and let cool slightly. Then, transfer to a cooling rack. Optional, sprinkle with flaky sea salt on top. Enjoy!