Stir cookie crumbs and margarine in a bowl until evenly moistened; press into the bottom of a 9-inch springform pan.
Bake in the preheated oven until lightly darkened, about 10 minutes. Remove from oven and cool to room temperature; about 30 minutes.
Stir gelatin and cold water in a small saucepan over low heat until gelatin dissolves completely, about 3 minutes.
Beat cream cheese and sugar with an electric mixer in a large bowl until smooth. Gradually add gelatin mixture, milk, and peppermint candy; mix until well-blended. Chill filling until thickened, about 2 hours.
Fold whipped cream and chocolate into filling. Pour filling into crust; chill until firm, about 1 hour.