Pulverize the Oreo cookies in a food processor until very fine. Fish out any cookies that aren't broken down by the blade. Transfer to a bowl and pour most of the butter over the cookie crumbs. Stir well to incorporate the butter. The crumbs should be cohesive when pressed together, but not wet. If you need to, add the remaining butter.

Spray or butter the springform pan. Dump in the cookie crumbs and press along the bottom and partially up the sides of the pan to create a nicely thick crust (about 1/4" thick). Don't worry about scraggly edges on the sides - it will all look cool when the pan sides come off.

Add the milk to a medium sized bowl, and sprinkle the gelatine evenly over the top. Give everything a stir and let sit while you prepare the rest of the filling.

Heat the cream, sugar, vanilla, and Kahlua in a small pan over medium-high heat. When the cream reaches a light boil, pour it over the milk/gelatine, and whisk together to break up clumps of the gelatine. Immediately add the chocolate and let stand for a few minutes, to melt the chocolate. Whisk the filling until very smooth (it will look like very rich hot chocolate).

Hold the sieve over crumb-pressed pan and pour the chocolate filling through it, slowly. Keep an eye on the level of the filling in the crust - you might not need all of the filling. Stop before the pie filling reaches the top 1/2" of the crust's edge. Cover the pan lightly with cling wrap, and refrigerate until set (about three hours).

To remove the ring from the pan, use a hair drier on high to gently warm the sides. Then, the ring will cleanly pop right off.

Use an electric mixer on high to beat the egg whites until light and foamy, about 2 minutes. Gradually add granulated sugar and continue beating until stiff, shiny peaks form, about 5 minutes. Gradually add powdered sugar and beat for several minutes more. The meringue will deflate slightly, but will its regain volume. The meringue should hold peaks when the whisk or beater is upended.

After the pie has fully set, spoon the meringue onto the pie use swirly gestures to create a stormy seas effect. Toast the meringue with a culinary torch, if desired. Store in the refrigerator until ready to use.