Mix the Dry Ingredients
In a large mixing bowl, combine crushed graham crackers, shredded coconut, mini marshmallows, and cocoa powder. Stir until evenly mixed.
Add Wet Ingredients
Pour in the melted butter, powdered sugar, and vanilla extract. Mix well until everything is fully incorporated.
Fold in Chocolate and Nuts
If using, gently fold in the chocolate chips and chopped nuts to evenly distribute them throughout the mixture.
Prepare the Baking Dish
Line an 8x8-inch baking dish with parchment paper, leaving extra overhang for easy removal.
Press and Chill
Firmly press the mixture into the prepared baking dish, spreading it evenly.
Cover with plastic wrap and refrigerate for at least 2 hours, or until firm.
Slice and Serve
Once set, lift the cake out of the dish using the parchment paper overhang.
Cut into squares or bars and enjoy!