Preheat your oven to 350 degrees F (175 degrees C). Line a 13x9-inch baking pan with foil, letting the edges hang over the sides for easy removal later.

In a medium bowl, combine the graham cracker crumbs, melted butter, and 3 tablespoons sugar. Stir until all the crumbs are evenly moistened.

Press this mixture firmly into the bottom of the prepared pan to create a scrumptious crust.

In a large mixing bowl fitted with a paddle attachment, beat the softened cream cheese, 1 cup sugar, and vanilla until smooth and creamy.

Sift in the flour and mix well, then add the eggs one at a time, mixing on low speed just until each is incorporated.

Gently fold in the semisweet chocolate chips using a rubber spatula.

Pour the cheesecake batter over the crust evenly and bake for about 30 minutes. The cheesecake should be nearly set but still slightly jiggly in the center.

Remove from the oven and sprinkle the chopped Hershey's chocolate bar, mini marshmallows, and coarsely chopped graham crackers evenly over the surface. Press the toppings down gently into the cheesecake.

Return to the oven and bake for an additional 10 minutes, or until the center is just about set.

Once completed, allow the cheesecake to cool completely at room temperature, then refrigerate for at least 4 hours to set fully.

When ready to enjoy, use the foil handles to lift the cheesecake slab from the pan, cut into bars, and serve!