Prepare the meat mixture: Combine the ground beef, pork rind crumbs, half of the BBQ rub, and the egg in a large bowl. Mix until all ingredients are well combined.
Divide and shape: Divide the meat mixture into 3 equal portions. Place one portion on a sheet of parchment paper.Fold the parchment paper over each side (total of 4 folds) to create straight edges, forming a rectangle.
Add fillings: In the center of each meat rectangle, arrange a layer of pepperoni slices and sprinkle generously with shredded mozzarella cheese.
Form the calzone: Using the parchment paper, carefully fold the meat over the fillings and roll slightly to form a tube shape.Press the edges firmly to seal the calzone completely. Repeat for the remaining portions.
Chill: Wrap each calzone tightly in parchment paper and refrigerate for 1 hour to help them maintain their shape during baking.
Bake: Preheat your oven to 370°F. Remove the calzones from the parchment paper and place them on a lined baking sheet. Season with the remaining BBQ rub and bake for approximately 40 minutes.