Preheat the oven to 375°F and coat a 12-inch oven-safe skillet with nonstick spray; a greased baking dish may be used as an alternative, though baking times can vary. Separate the biscuits and place them onto a clean surface. Flatten each one to a thickness of approximately ⅛ inch using a rolling pin. Spoon about 1 tablespoon of pizza sauce onto each biscuit, then add 1 tablespoon of pepperoni slices and 2 cubes of mozzarella. Bring the edges together over the filling and pinch tightly to seal completely, ensuring there are no openings. Arrange the sealed biscuits seam side down into the prepared skillet. Repeat with the remaining dough and filling. Transfer the skillet to the oven and bake for 20 to 22 minutes, or until the tops are richly golden.

While the pizza bombs bake, stir together melted butter, garlic salt, Italian seasoning, and grated parmesan in a small bowl. When the bombs are finished baking, immediately brush the tops with the prepared garlic butter mixture. Serve warm alongside the reserved pizza sauce for dipping.