Garnish: Preheat broiler. Whip cream until stiff peaks form; refrigerate.
Place 2 graham crackers on a small baking sheet. Top each with chocolate, then 2 marshmallow halves. Broil for 30 to 60 seconds on the center rack or until marshmallows are golden. Top with remaining 2 crackers.
Milkshake: In a blender, combine ice cream and milk until frothy. If you’d like thicker milkshakes, add more ice cream and whirl again.
Spoon chocolate sauce onto a small plate. Place cookie crumbs on another small plate. Roll rim of 1 milkshake glass in the chocolate sauce then rim with crumbs. Repeat with another milkshake glass.
Using a spoon, drizzle half the sauce in 4 spots down the inside of one of the glasses (to form stripes). Fill glass with the shake. Repeat with remaining glass.
Top with whipped cream then stand a s’more in each shake. Sprinkle with any remaining cookie crumbs. Serve with a spoon.