Lightly spray a 10-inch pie dish with cooking spray. Set pan aside.

Place the Oreos in the bowl of a food processor and process until they become fine crumbs. Add the butter and salt and mix to combine. Press into the bottom and up the sides of the prepared dish, then freeze for 20 minutes.

Combine the ice cream and Heath bars in a medium mixing bowl and stir until candy is evenly distributed. Gently spread into frozen crust and smooth the top with a rubber spatula. Return to freezer for 20 minutes.

Heat the fudge sauce until it is pourable but not hot—you don’t want to melt the ice cream. Spread over the frozen ice cream layer and return to freezer while you make the whipped cream. (Some brands are a little harder to spread than others—you don’t have to have a perfectly thin layer.)

Place the heavy cream and powdered sugar in the bowl of a stand mixer fitted with the whisk attachment. Whip until soft peaks form, then add Kahlua (if using) and beat until it holds stiff peaks. Spread over the hot fudge layer. Top with chocolate curls or chopped Heath bars and cover with plastic wrap. Freeze at least 4 hours or overnight. Remove from freezer 10 to 20 minutes before serving to ease slicing.