Place a few tablespoons of sweetened condensed milk into a small dish with a rim. Place graham cracker crumbs in a small dish with a rim. Place the rim of the glass into the sweetened condensed milk, then the crumbs. Place glasses in freezer until ready to use.
Milkshake
Place all ingredients into high-powered blender and combine. Divide between glasses. Garnish with whipped cream, graham cracker crumbs, graham cracker pieces and lime zest