This dessert is true frozen bliss. The recipe has been in my family for years. We compare all other desserts against it, and nothing, ever, has measured up. I make this all-year long, but it's especially great in the summer because it's quick and easy to assemble (no baking required) and feeds a crowd. —EmilyC
For crust: Butter the bottom of a 9x13x2 pan (such as Pyrex). Melt 1/2 stick butter (4 tablespoons) in a bowl. Crush the Oreo cookies into fine crumbs with a little texture. (For ease, place the cookies in a zipper-lock bag, seal, and then crush with a rolling pin. Turn the bag inside-out to scrape out all of the crumbs.) Mix the Oreo crumbs with the melted butter in the pan, and press them evenly into the bottom. Cover the pan and freeze until the crust is set, about 30 minutes.
For filling: Let the ice cream soften a bit on the counter until it's spreadable. Evenly spread it over the Oreo crust. Cover the pan and return to the freezer for at least an hour to set the ice cream.
For fudge topping: Combine the remaining stick of butter (8 tablespoons), chocolate, sugar, and evaporated milk in a saucepan. Bring to a low boil and cook for 4 minutes, stirring constantly. Cool to room temperature. (If in a hurry, set the saucepan in a ice bath to speed up the cooling process, stirring several times and scraping down the sides of the bowl. It should be ready in 5 to 10 minutes.) Working quickly, pour the fudge evenly over the ice cream, covering as much as possible, then spread with a knife to distribute the fudge in a smooth, even layer. Cover the pan and return to the freezer for another hour or two, or until fully frozen and set.
When ready to serve, let the Oreo dessert sit on the counter for about 5 minutes to take the chill off (and make cutting easier), then cut into squares and serve. Tightly covered, it'll keep well in the freezer for several weeks.