Preheat your oven to 400°F (200°C).

In a large mixing bowl, combine flour, baking powder, and salt. Mix well. Add cold, cubed butter and mix until it resembles coarse crumbs. Stir in mozzarella cheese and pepperoni. Gradually add cold water until the dough comes together. Knead gently for about 1 minute until smooth.

Roll out the dough into a rectangle about 1/4 inch thick. Cut into smaller rectangles, approximately 3x4 inches. Place a spoonful of pizza sauce and a few pepperoni slices in the center of each rectangle. Fold the dough over to create a pocket and seal the edges.

Brush the tops of the rolls with beaten egg and sprinkle with Italian seasoning if desired. Bake for 15-20 minutes or until golden brown.

Let the rolls cool slightly before serving with extra pizza sauce for dipping.