Set Masterbuilt Gravity Series to 350°F.
In a well buttered cake pan or disposable aluminum tray, arrange graham crackers along the bottom and sides, covering all areas.
Cover the crackers completely with chocolate squares.
Arrange marshmallows standing up throughout the entire pan.
Add casserole into your Gravity Series for 20-30 minutes, or until the marshmallows are well toasted.
Remove and allow to rest for 20 minutes.
Garnish the casserole with a drizzle of chocolate sauce, cocoa powder, and powdered sugar.
Cut into squares and serve immediately.