Measure out all your ingredients and preheat the oven to 350F.
Line a baking sheet with a silicone baking mat.
In a medium sized mixing bowl, stir together the flour, powdered sugar, baking powder, and salt.
Mix in the chunky peanut butter until it is all combined and resembles course, peanut buttery sand.
Gradually add in the olive oil, mixing until a dough forms that is slightly sticky. It is best to just jump in and mix with your hands. Add a little at a time and incorporate all before you add any more in. You want to be able to easily form the dough into a ball without it being too crumbly, but also not have so much oil in the dough that it melts everywhere.
Roll a spoonful of dough into a ball. Place on the prepared baking sheet. Repeat with remaining dough.
Place a peanut in the middle of each cookie.
In a small bowl, whisk together the egg yolk and the teaspoon of water to create an egg wash.
Brush the cookies with the egg wash.
Bake for 15 minutes.
Allow to sit for at least 10 minutes on the cookie sheet. They will be fragile and super hot fresh out of the oven.
Move to a wire cooling rack to cool completely.
Notes
These cookies will last up to two weeks when stored in an air-tight container at room temperature.