Instructions

• In the bowl of a stand mixer fitted with the paddle attachment (or a large bowl and electric hand mixer), combine 1 large egg, ½ cup softened unsalted butter, ½ cup granulated sugar, ½ cup packed light brown sugar, and 2 teaspoons vanilla extract. Cream on medium-high speed until the mixture is light and fluffy, about 5 minutes.
• Stop the mixer and scrape down the sides and bottom of the bowl with a spatula.
• Add 1 ¾ cups cake flour, 2 teaspoons cornstarch, ¼ teaspoon baking powder, ¼ teaspoon baking soda, and a pinch of salt (optional). Mix on low speed until just incorporated, about 1 minute. Do not overmix.
• Add the entire 10-ounce bag of Reese’s Peanut Butter Chips and mix on low just until the chips are evenly distributed and no streaks of flour remain. The dough will be sticky and tacky.
• Using a medium 2-inch cookie scoop, portion heaping 2-tablespoon mounds of dough (about 13 mounds). Place the mounds on a large plate or baking sheet, flatten each mound slightly with your hand or the back of a spoon, cover with plastic wrap, and refrigerate for at least 3 hours and up to 5 days. Do not bake while the dough is warm.
• When you are ready to bake, preheat the oven to 350°F (177°C). Line a baking sheet with a Silpat or lightly grease the sheet with cooking spray.
• Arrange the chilled dough mounds on the prepared baking sheet, spacing them at least 2 inches apart (about 8 cookies per sheet).
• Bake for about 8 to 9 minutes, or until the cookie edges have set and the tops are just beginning to set (they may still look slightly pale and glossy in the center). Do not overbake—the cookies will firm up as they cool.
• Remove the baking sheet from the oven and let the cookies cool on the sheet for about 5 minutes, then transfer the cookies to a wire rack to finish cooling.
• While the cookies cool, make the frosting: in the bowl of a stand mixer fitted with the paddle attachment (or a large bowl and electric hand mixer), beat ⅓ cup creamy peanut butter and ¼ cup softened unsalted butter on medium-high speed until light and fluffy, about 3 minutes.
• With the mixer on low, slowly add 1 ½ cups confectioner’s sugar and a pinch of salt (optional). Mix until the frosting comes together and is smooth.
• Add a splash of cream or milk as needed to reach a spreadable consistency (about 1 1/2 tablespoons cream was used in the original). Mix briefly to combine.
• Add a generous dollop of frosting (about 2 tablespoons) to each cooled cookie and smooth with a knife or offset spatula.
• Optionally garnish with chocolate sprinkles. Serve immediately.