Line a 9x9 inch baking dish with plastic wrap. Make sure to leave enough overhang to easily lift up the squares when they're done. Line the bottom of the baking dish with graham crackers, you may have to break a few up to cover the corners or sides. Set aside.
In a mixing bowl combine heavy cream, lime juice, lime zest and powdered sugar together and beat with an electric mixer on high speed for a few minutes until stiff peaks from, mixutre should resemble stiff whipped cream.
Use a spoon or spatula to pour the heavy cream mixture over the bottom layer of graham crackers. Smooth mixture out evenly. Cover the top with graham crackers the same way to lined the bottom. Cover the whole dish with plastic wrap and allow squares to freeze for at least 6 hours or up to overnight.
When completely frozen remove from the freezer and cut into squares, return them to the freezer so they don't melt while you prep the chocolate and graham cracker crumbs.
Melt the chocolate using a microwave or a double broiler, set aside once completely melted and smooth. Crush remaining graham crackers into fine crumbs. Pour them into a bowl and toss with melted butter and a few pinches of salt.
Grab the squares and garnish them however you like; dip in the chocolate, covered with graham crack crumbs, drizzle chocolate over them, it's completely up to you!
Serve immediately or freeze until ready to serve.