1 cup creamy peanut butter
1 cup light brown sugar, packed
1 large egg
1 tablespoon vanilla extract
1 teaspoon baking soda
6 ounces semi-sweet, dark, or bittersweet chocolate, chopped
To the mixing bowl of a stand mixer fitted with the paddle attachment, combine peanut butter, brown sugar, egg, vanilla, and beat on medium-high speed until well-combined and the sugar is fully incorporated and is mixture is no longer gritty or granular, about 3 minutes. Stop to scrape down the bowl as necessary.
Add the baking soda and beat to incorporate. Add the chocolate and beat to just incorporate; don't overmix or the nice chocolate chunks will break down. Transfer dough to airtight container and refrigerate for at least 2 hours, and up to 5 days, before baking.
Preheat oven to 350F, line 2 baking sheets with Silpat Non-Stick Baking Mats, parchment, or spray with cooking spray; set aside. Using a 2-inch cookie scoop (about 2 tablespoons of dough or about 1.60 to 1.75 ounces by weight), form dough mounds and place on prepared baking sheet, spaced 2 inches apart (8 to 10 per tray). If chocolate is falling out of dough since there is an abundance, roll ball between palms to encourage it to stay in the dough. Slightly flatten the mounds before baking so they don't stay too domed and puffed while baking, just don't over-flatten.
Bake for 8 to10 minutes, until edges are set and tops are barely set, even if slightly underbaked in the center. Watch them very closely after 7 minutes and I recommend not baking longer than ten minutes. Cookies firm up as they cool, and baking too long will result in cookies that become too crisp and hard (The cookies shown in the photos were baked for 8 minutes, with trays rotated at the 4-minute mark, and have chewy edges with pillowy soft centers). Allow cookies to cool on the baking sheet for 5 to 10 minutes before removing and transferring to a rack to finish cooling. Store cookies in an airtight container at room temperature for up to 1 week, or in the freezer for up to 3 months. Alternatively, unbaked cookie dough can be stored in an airtight container in the refrigerator for up to 5 days, so consider baking only as many cookies as desired and save the remaining dough to be baked in the future when desired.