Mix your butter, parmesan, parsley, garlic and salt until you have a smooth paste. Spread this mixture over a rectangular piece of pizza dough. Roll up into a sausage. Cut into even pieces then place next to each other, cut side up, in a lined baking dish. Brush with egg then bake for 20 minutes at 180°C. Leave to cool slightly, then cut the buns in half in an even layer.
Top the bottom half of the buns with pizza sauce, mozzarella and pepperoni slices. Grill for 5 minutes or so, or until crisp and melted.
