Preheat the oven to 350 degrees. Spray a 13- by 9-inch baking dish with cooking spray. Line the pan with foil, allowing several inches to hang over the edges. Spray the foil lightly with cooking spray and set pan aside.

Place the Oreos in the bowl of a food processor and process until the cookies are fine crumbs. Add the melted butter and process again until fully combined. (Or put the cookies in a large zip-top plastic bag and crush them with a rolling pin, then place in a bowl and stir in the butter.)

Press the mixture into an even layer in the bottom of the prepared baking dish. Bake for 5 minutes. Remove from the oven and cool for 20 minutes, then make the filling.

Stir the sweetened condensed milk, coconut, vanilla, and salt together in a mixing bowl. Spread into an even layer over the crust—damp fingertips are helpful here.

Return to the oven for 20 to 25 minutes, until the coconut layer is golden around the edges. Set the pan on a wire rack to cool for completely.

Once your bars have cooled to room temperature, put the chocolate chips in a medium heat-proof bowl.

Heat the heavy cream in a small saucepan until it just begins to steam. Pour the cream over the chocolate chips and let it sit for 3 minutes.

Whisk the chocolate and cream together until the chocolate is melted and the mixture is smooth. Spread the topping over the cooled bars and refrigerate for 20 minutes, or until the chocolate is set. Slice into bars and serve.