Prepare crust. Preheat oven to 350ºF. Grease 9-inch square baking pan with nonstick cooking spray.
In large mixing bowl, combine cookie crumbs and melted butter until mixture holds together. Fill prepared pan with crumb mixture and press into bottom and sides of pan to form even crust.
Bake in preheated oven until lightly browned, 10 to 12 minutes. Remove pan from oven and set aside to cool completely. Freeze until ready to use.
Scoop chocolate ice cream into prepared crust, smoothing top with offset spatula. (This works best if ice cream is thawed a few minutes beforehand.) Return to freezer until firm, at least 30 minutes.
To prepare meringue, in stand mixer fitted with whisk attachment, beat egg whites on low speed until foamy, about 1 minute. Add cream of tartar and increase speed to medium until they hold soft peaks. Gradually add sugar followed by vanilla extract and beat on high speed until it forms stiff, glossy peaks, about 5 more minutes.
Cover pie with meringue and return to freezer until ready to serve.