Preheat oven to 350 degrees.

Prepare an 8x8 baking dish with parchment.

Mix together graham cracker crumbs, ¼ cup sugar, and butter.

Press down into the baking dish and bake for 8-10 minutes.

Let the crust cool completely.

In an bowl of an electric mixer, place the cold water.

Sprinkle gelatin over the water and let it stand for 10 minutes.

In a medium saucepan, mix sugar, corn syrup and ¼ cup water.

Bring the mixture to a boil over medium-high heat.

Attach a candy thermometer and let this mixture cook until it reaches 240 degrees.

Once this mixture reaches 240 degrees, turn the electric mixer on low and slowly pour over gelatin.

Once all the mixture is in the mixer bowl, turn it up to high and let it mix for 8-10 minutes or until doubled in size.

Add vanilla and mix for another minute.

Pour this mixture over the cooled crust and let it rest, uncovered for 8 hours or overnight.

Melt together chocolate and butter in microwave or in a double boiler.

Pour over marshmallow and allow to cool completely.