Preheat the oven to 400°F (200°C). Line two baking sheets with parchment paper. Keep the puff pastry chilled until ready to cut.

Stir the oregano and garlic powder into the thick pizza sauce. In a separate small bowl, beat the egg with the water to make an egg wash.

On a lightly floured surface, work with one puff pastry sheet at a time. Cut a strip about 2 inches (5 cm) wide from one edge of each sheet and reserve it for bandages. Cut each larger remaining piece into six roughly equal rectangles (two rows by three columns), making 12 bases in total. Cut the reserved dough into strips about 1/4 inch (6 mm) wide, then trim into lengths that fit across the bases.

Arrange the 12 pastry rectangles on the prepared sheets, leaving at least 1 inch (2.5 cm) between them. Spread roughly 2 teaspoons of seasoned pizza sauce onto each rectangle, leaving a 1/4-inch (6 mm) border.

Place two pepperoni slices on each base and divide the shredded mozzarella evenly over the tops, keeping most of the cheese inside the border.

Lay three or four short pastry strips diagonally over each pizza to resemble mummy bandages. Gently press the strip ends onto the exposed pastry border. Leave a small opening near the upper third for the eyes, then lightly brush only the exposed pastry and bandages with egg wash.

Bake for 16–18 minutes, rotating the pans halfway through, until the pastry is well puffed and deeply golden and the cheese is bubbling. If baking both trays at once, swap their rack positions halfway through.

While the pizzas are still warm, press two black olive rings into the exposed melted cheese on each mummy to create eyes. Allow to stand briefly, then serve warm.