3/4 cup old-fashioned oats
3/4 cup all-purpose flour
1/2 teaspoon fine salt
1/2 teaspoon baking soda
1/4 teaspoon baking powder
8 tablespoons unsalted butter (1 stick), at room temperature
1/2 cup natural chunky peanut butter, no sugar added
1/2 cup granulated sugar
1/2 cup packed light brown sugar
1 large egg, at room temperature
1 teaspoon vanilla extract
1 cup coarsely chopped bittersweet chocolate
Heat the oven to 350°F and arrange a rack in the middle. Line a baking sheet with parchment paper and set aside. Place oats in the bowl of a food processor and pulse several times until they are about half powder and half small flakes. Transfer oats to a large bowl, add flour, salt, baking soda, and baking powder, stir to combine, and set aside.
Combine butter, peanut butter, and both sugars in the bowl of a stand mixer fitted with a paddle attachment and mix on medium speed until light and fluffy, about 2 minutes. Scrape down the sides of the bowl, add egg and vanilla, and beat until smooth, about 30 seconds. Add oat mixture and mix on low speed until dough comes together. Add chocolate and mix on low speed for a few seconds until just incorporated.
Scoop dough by rounded tablespoons onto the parchment-paper-lined baking sheet. Bake until the cookies are golden brown at the edges but still soft in the center, about 10 to 13 minutes. Remove from the oven and let sit on the baking sheet for a few minutes before transferring to a rack to cool completely.