Start by beating together ½ cup of softened unsalted butter and ½ cup of creamy peanut butter in a large mixing bowl until smooth and creamy, about 2-3 minutes.

Add ½ cup granulated sugar, ½ cup brown sugar, 1 large egg, and 1 teaspoon of vanilla extract, mixing well until fully combined and fluffy.

In a separate bowl, whisk together 1 ½ cups of all-purpose flour, 1 teaspoon of baking soda, and ½ teaspoon of salt.

Gradually add this dry mixture to the wet ingredients, mixing on low speed until a soft dough forms.

Preheat your oven to 350°F (175°C) while you prepare the cookies.

Scoop tablespoon-sized portions of the cookie dough onto a parchment-lined baking sheet, leaving space between each scoop.

Flatten each dough ball slightly, then sprinkle the tops with a bit of extra granulated sugar.

Place the baking sheet in the preheated oven and bake for approximately 10 minutes. Watch for the edges to become lightly golden.

Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.

Prepare the filling by beating together ¼ cup of softened unsalted butter and ½ cup of creamy peanut butter in a medium bowl until fluffy.

Gradually mix in 1 cup of powdered sugar and add 1 teaspoon of vanilla extract, adjusting the consistency with milk as needed.

To assemble, spread or pipe the peanut butter filling onto the flat side of one cookie and place another cookie on top.