Preheat the Oven: Set your oven to 350°F (175°C) and let it warm up while you prepare the cookie dough.

Mix the Ingredients: In a large bowl, combine the peanut butter, granulated sugar, and brown sugar. Using an electric mixer, beat on medium speed until smooth and creamy, about 2 minutes.

Add Egg and Vanilla: Beat in the egg and vanilla extract until well incorporated. Scrape down the sides of the bowl to ensure even mixing.

Incorporate Dry Ingredients: In a separate bowl, whisk together the baking soda and salt. Gradually add this mix to the peanut butter mixture, blending until combined.

Form the Cookies: Using a tablespoon, scoop out the dough, roll it into balls, and place them 2 inches apart on a parchment-lined baking sheet. Flatten each ball slightly with a fork to create that signature crisscross pattern.

Bake: Bake the cookies in the preheated oven for 10-12 minutes, or until the edges are lightly browned. The centers will look soft; they’ll continue to firm up as they cool.

Frost the Cookies: Let the cookies cool completely before frosting. To make the frosting, cream the softened butter, powdered sugar, milk, and vanilla together until smooth. Once the cookies are cool, spread the frosting generously on top of each cookie.