Preheat oven to 350 degrees. Spray a 9-inch square baking pan with cooking spray then line with foil or parchment paper, leaving an overhang around the edges. Spray foil lightly with cooking spray and set pan aside.

Process Oreos in the food processor until they form fine crumbs. Pour melted butter into the prepared pan and sprinkle with the cookie crumbs. Pack the crumbs into an even layer in the bottom of the pan. Sprinkle with the pecans, caramel bits, toffee bits, and chocolate chips. Stir the espresso powder into the condensed milk until the powder dissolves, then pour in an even layer over the cookie bars.

Bake until the top is golden and the edges bubble, 25 to 28 minutes. Place pan on a wire rack to cool completely, 1 hour. Once cool, use the foil to remove the cookies from the pan and transfer to a cutting board. Remove foil, slice into bars, then serve and enjoy. (They are very gooey so I recommend refrigerating before slicing and serving.)