For the choux pastry:

1. Preheat oven to 425°F. Line a large baking sheet with a silicone baking mat or parchment paper.
2. In a heavy bottom saucepan, combine the water, butter, salt, and sugar, and bring to a boil until the butter melts.
3. Remove from heat and pour in the flour all at once, and, with a wooden spoon or silicone spatula, stir vigorously until the flour in incorporated. Place back on medium heat and continue vigorously stirring (yes, this is a mini arm workout!) until the dough comes together as a ball, and a thin film starts to form on the bottom of the pan.
4. Remove from the heat and make a well in the center of the dough. Add in one egg and vigorously stir until it is completely combined. Repeat with the other three eggs.
5. Using a large cookie scoop (a 3 tablespoon-sized model), scoop the dough onto the prepared baking sheet, about an inch or two apart.
6. Bake for 15 minutes, until they begin to turn golden. Turn the oven down to 350°F and bake for 15 more minutes. Turn the oven off, crack the door, and allow them to rest in the oven for 10 minutes before removing to cool further.

For the chocolate ganache:

1. In a medium bowl, combine the chocolate and salt.
2. Either in the microwave, or on the stove, heat the cream to a simmer. Pour the warm cream over the chocolate. Allow it to sit for a minute, then stir until it is smooth and creamy.

To assemble:

1. Scoop the marshmallow fluff into a pastry bag fitted with a small or medium tip of any shape. Stab the tip into the side of the cream puff, and fill with fluff (really as much as you want).
2. Dip the topside of the filled puffs into the chocolate ganache and allow any excess to drip off.
3. Sprinkle the chocolate with the graham cracker crumbs before it sets.