Line an 8x8-inch square baking dish with parchment paper, leaving an overhang on the sides for easy removal.
Place 4 graham cracker sheets (split into 8 squares) in a single layer across the bottom of the prepared dish.
Combine the chocolate chips and coconut oil in a microwave-safe bowl. Heat in 30-second intervals, stirring between each, until the chocolate is completely melted and smooth.
Pour the melted chocolate over the graham cracker base and spread into an even layer using a spatula. Place the dish in the freezer for 5 to 10 minutes to allow the chocolate to set.
In a separate mixing bowl, add the thawed whipped topping and the protein powder. Gently fold the protein powder into the whip until fully incorporated and no powder streaks remain.
Spread the whipped protein mixture evenly over the hardened chocolate layer.
Top with the remaining 4 graham cracker sheets (8 squares), aligning them directly over the bottom squares to facilitate easier cutting.
Transfer the dish to the freezer for at least 1 hour, or until the filling is firm and set.
Lift the parchment paper to remove the bars from the dish. Use a sharp knife to slice through the layers into 8 individual frozen s'mores sandwiches.
Serve immediately or store in an airtight container in the freezer.