Preheat your oven to 375°F (190°C) and line your baking sheets with parchment paper.

In a medium bowl, whisk together the flour, baking soda, and salt.

In a large bowl or the bowl of your stand mixer, cream together softened butter, granulated sugar, and brown sugar until light and fluffy.

Beat in the vanilla extract and add the eggs one at a time, mixing well after each addition.

Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined.

Fold in the chocolate chips until evenly distributed.

Drop rounded tablespoons of dough onto the prepared baking sheets, leaving about 2 inches between each cookie.

Bake for 9-11 minutes or until the edges are golden brown and the centers are slightly soft.

Let the cookies cool on the baking sheets for a few minutes before transferring them to a wire rack to cool completely.

In a large bowl, cream together the softened butter and peanut butter until smooth and creamy.

Gradually add powdered sugar, one cup at a time, mixing on low speed until combined.

Add the milk and vanilla extract and beat until the filling is light and fluffy.

Add a pinch of salt to balance the sweetness.

Find cookies that are similar in size and shape.

Spread a generous amount of peanut butter filling on the flat side of one cookie.

Top with the flat side of another cookie, pressing down gently to create a sandwich.

(Optional) Roll the edges of the cookie sandwiches in sprinkles, chopped nuts, or mini chocolate chips.

(Optional) Chill the cookie sandwiches in the refrigerator for about 30 minutes before serving.

Serve immediately or store in an airtight container in the refrigerator for up to 3 days.