It is amazing how much boys grow when they are 12, 13, 14. Amazing.
In a small bowl, combine wafer crumbs and sugar; stir in butter. Press onto the bottom and 1-1/2 in. up the sides of a greased 9-in. springform pan. Place pan on a double thickness of heavy-duty foil (about 18 in. square); securely wrap foil around pan. Place pan on a baking sheet. Bake at 325° for 12 minutes. Cool on a wire rack.
In a large bowl, beat the cream cheese, milk, chocolate syrup and vanilla until smooth. Add eggs; beat just until combined. Stir in 2-1/2 cups chopped candy bars. Pour into crust. Place springform pan in a large baking pan; add 1 in. of hot water to larger pan.
Bake at 325° for 75-80 minutes or until center is just set and top appears dull. Remove springform pan from water bath. Cool on a wire rack for 10 minutes. Carefully run a knife around edge of pan to loosen; cool 1 hour longer. Refrigerate overnight.
Top with remaining chopped candy bars; drizzle with additional chocolate syrup.