Preheat oven to 300°F. Wrap outside bottom and side of 9-inch springform pan with heavy-duty foil to prevent leaking. Lightly spray inside bottom and sides of pan with cooking spray. Combine cookie crumbs and next 3 ingredients in a bowl with a pastry blender until crumbly. Press mixture into bottom of pan. Bake 12 minutes or until set. Cool crust on a wire rack 10 minutes.

Meanwhile, beat cream cheese, 11/4 cups sugar, flour, and vanilla at medium speed with an electric mixer until light and fluffy. Beat in eggs, 1 at a time, just until blended. Beat in melted chocolate. Pour over crust.

Bake at 300°F for 1 hour and 15 minutes or until almost set. Turn oven off. Let cheesecake stand in oven, with oven door open at least 4 inches, for 30 minutes. Remove from oven, and gently run a knife around outer edge of cheesecake to loosen from sides of pan. (Do not remove sides of pan.) Sprinkle with marshmallows. Cool on a wire rack 30 minutes. Sprinkle with pecans.

Microwave frosting in a small, microwave-safe bowl at HIGH 15 seconds or until pourable. Drizzle frosting over marshmallows and pecans. Refrigerate at least 6 hours or overnight.

To serve, run small metal spatula around edge of pan; carefully remove foil and sides of pan.