Combine chocolate and heavy cream in a microwave-safe bowl and heat on high for 2½ minutes. Stir until the chocolate is melted and you have a gorgeous ganache!
Pour into a 9" prepared graham cracker crust.
Cover with plastic wrap and park in the fridge for at least 4 hours or overnight.
Cut marshmallows in half on the bias. Place the marshmallows cut side down on the chilled pie.
Pre-heat broiler and pop in the oven for about 1 minute, rotating pan and watching closely so the marshmallows don't burn. Let cool and cover with plastic wrap. Chill for another hour or two to let ganache set again.
Slice and serve. This pie is so rich and delicious, a small slice will satisfy your sweet tooth.