Preheat the oven to 350 degrees. Spray an 9-inch square baking pan with cooking spray and set aside.

Combine the cream cheese, sweetened condensed milk, egg, vanilla, and salt in a large mixing bowl. Beat with an electric mixer set to medium speed until very smooth and creamy, about 3 minutes. Fold in the chopped peanut butter cups.

Press two-thirds to three-quarters of the cookie dough into the bottom of the prepared pans—enough to cover the bottom in an even layer. Pour the cheesecake mixture evenly over the cookie layer and smooth the top with a rubber spatula. Break up remaining cookie dough into small pieces and sprinkle over the cheesecake layer.

Bake until slightly browned on top, 30 to 35 minutes. Set pan on a wire rack and cool fully.

Combine all ingredients in the top of a double boiler set over barely simmering water. Stir until butter and chocolate are melted and smooth. Remove pan from the heat and stir chocolate mixture for 1 minute to cool it down slightly. Pour over cooled cheesecake bars and smooth with an offset spatula. Refrigerate for at least 1 hour, or until glaze sets, before cutting into bars and serving.

(Uneaten bars can be stored in an airtight container at room temperature for up to 3 days or in the fridge up to 2 weeks. In the freezer they last a few months.)