Preheat the oven to 350°F. Combine the peanut butter, sugar, and egg in a bowl. Stir together until well combined.
Scoop onto a parchment-lined baking sheet. (Roll into 1" balls with your hands, if you do not have a scoop.) Press down with the back of a fork, and then press again from the opposite direction, to form the criss-cross pattern on top.
These cookies will not spread much at all. You can bake the full recipe on a single tray if you like. Bake for 12 minutes and then cool on the tray for 1-2 minutes before transferring to a wire rack to finish cooling. Store in an airtight container.
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Notes
I like to remove about 2 tablespoons of peanut butter from the "cup" listed in this recipe. This results in a cookie that spreads out nicely and is slightly less dense. Friends and family universally love this cookie even more than the original.