Preheat your oven to 350°F. Line a 9x13-inch baking pan with foil, then coat it lightly with nonstick cooking spray for easy removal later.

In a large bowl, mix together the melted butter, granulated sugar, and light brown sugar until smooth. Add the eggs one at a time, ensuring each is fully incorporated. Stir in the vanilla extract, salt, and baking soda.

Gradually fold in the all-purpose flour, mixing just until combined. Gently stir in the chocolate chips.

In a small separate bowl, combine the sweetened condensed milk and creamy peanut butter. Stir until the mixture is smooth.

Press half of the cookie dough into the bottom of the prepared baking pan, using your hands (sprayed with cooking spray) to flatten it evenly. Arrange the miniature peanut butter cups over the dough in an even layer.

Carefully pour the sweetened condensed milk and peanut butter mixture over the peanut butter cups, leaving about a 1/4-inch border around the edges to prevent the milk from touching the foil.

Break apart the remaining cookie dough and scatter it over the milk layer. Press the dough gently to flatten, ensuring it covers most of the bottom layer, though some gaps are fine.

Bake for 30 to 35 minutes, or until the tops are just beginning to turn golden brown. Allow the bars to cool completely in the pan before cutting them into squares.

Store the bars in an airtight container at room temperature for up to 3 days, or freeze them for up to 1 month. Serve at room temperature for the best texture.