Line a 9x9 inch square baking dish/pan with plastic wrap. Make sure to leave enough over the sides to make it easier to take the bars out of the pan once they're frozen.
Layer the bottom of the baking pan with a single layer of graham crackers. You may have to break a few up into smaller pieces to fit the corners and the sides. Set aside.
In a bowl combine heavy cream, powdered sugar & vanilla extract. Using an electric mixer beat the ingredients on high speed for a few minutes until stiff speaks form, you're basically looking for the texture of whipped cream. Pour the mixture over the graham crackers and spread out evenly using a spatula, make sure to cover all the crackers. Lay a single layer of graham crackers over the top of the whipped cream mixture. Just like the bottom layer, you may have to break up a few smaller pieces to fit corners & the sides.
Place the pan in the freezer for at least 6 hours or up to over night.
When completely frozen remove from the freezer and life the sandwiches up from the pan using the plastic wrap. Cut into squares. You can either serve them as is or roll them in sprinkles, cookie crumbs, coat them in melted chocolate, whatever you like.