Add enough oil to a large frying pan so that oil is about 1/2 inch deep. Heat for several minutes over high heat until very hot. Reduce to medium-high heat.
While oil is heating, use a round 1-inch cookie cutter to cut the centers out of the biscuits to make donuts. Discard the donut "holes" (or you can fry them and dip in chocolate and graham crackers along with the regular-sized donuts).
Use tongs to place donuts in the oil, cook for 1-2 minutes until bottoms are browned, then flip and cook another 1-2 minutes until completely golden. Transfer to a paper-towel lined plate or cooling rack and repeat with remaining donuts.
While donuts are cooling, place chocolate in a microwave-safe bowl and microwave on half power for 1 minute, then 20 seconds more at a time, stirring after each until smooth.
Dip donuts in the melted chocolate to cover one half of the donut. Top with marshmallows and sprinkle with crushed graham crackers.
Place donuts on a baking sheet. Broil in the oven for 1-3 minutes until marshmallows are golden brown. (Watch very closely so they don't burn!!!)
Serve immediately or allow to cool completely, then store on a plate covered in plastic wrap for up to 24 hours.