Shmear about 3 inches of the outside of each jar, at the top, with a thick layer of chocolate frosting and vanilla frosting. The more the merrier!
Roll frosted cup in sprinkles and stick broken cookies to the cup.
In a blender or with a bowl and spoon, mix chocolate ice cream with milk to a thick and drinkable consistency. Divide among jars. Pour thick layer of syrup on top of chocolate ice cream.
In a blender or with a bowl and spoon, mix vanilla ice cream with milk to a thick and drinkable consistency. Divide among jars.
Add a thin layer of chocolate sauce. Top with seltzer to make a soda layer.
Pile on tons of whipped cream and a top each shake with black and white cookie, chocolate bark, and chocolate shavings. Serve immediately with a straw and a spoon.