In the bowl of a stand mixer, place the powdered unflavored gelatin with 3/4 cup cold water. Let sit.
In a small sized pot, combine the sugar, corn syrup and remaining 1/2 cup of water. Heat over medium and bring to a boil. Once boiling, raise heat to high and cook until the mixture reaches 240 degrees.
Using a fine mesh sieve, completely cover the bottom of an 8-inch square baking pan with a solid layer of powdered sugar. Have three bowls and three spoons ready before whipping the marshmallow.
Turn stand mixer to low and carefully pour the hot sugar mixture into the gelatin. Turn the speed up to high and whip for 5 to 7 minutes. Add vanilla and mix till combined.
Once you have whipped the mixture, quickly pour 1/4 of the mixture into one small bowl and add blue gel food coloring, 1/4 of the mixture into another and add red food coloring, and leave 1/2 of of the mixture white. Work quickly as the mixture will set fast.
Pour blobs of the 3 different colored marshmallow randomly into the dish till the dish is full and all of the marshmallow is in the dish. Try to keep the white between the blue and red.
Using a stick of any kind (a chopstick works perfectly!), begin to swirl the colors into each other, careful not to completely mix the colors together. This is the fun part! Every batch will be different.
With the fine mesh sieve, cover generously with powdered sugar and flatten the surface with your hands. Let sit uncovered overnight to set.
Run a knife along the edges. Remove the marshmallows from the pan and cut into squares. Dust with powdered sugar to reduce stickiness.
Roast a marshmallow over the fire (or melt it slightly in the microwave if you don't have a fire!) and sandwich with DOVE chocolate and two graham crackers.