Divide bread dough into 4 balls. Place on a flat work surface; cover with plastic wrap sprayed with cooking spray. Let stand until room temperature and pliable, about 30 minutes.
Preheat oven to 350 degrees F (175 degrees C).
Dust work surface with flour and roll out dough into 8-inch circles. Transfer to baking sheets lined with parchment paper.
Mix pizza sauce and tomato paste together in a bowl. Spread 2 tablespoons of the sauce mixture over each circle, leaving a 1-inch border.
Arrange 15 pepperoni slices and 1/2 cup mozzarella cheese over one half of each circle. Fold circles in half over pepperoni and cheese; pinch edges and fold to seal.
Whisk egg white and water together in a small bowl. Brush over top of dough.
Bake in the preheated oven until golden brown, about 30 minutes.
