Preheat oven to 425℉. Line a rimmed baking sheet with parchment paper.
Roll out your thawed puff pastry with a rolling pin. Gently poke it allover with a fork. Score the outer edge 0.5 inches in with a pairing knife. Place it onto your baking sheet and brush it ALL OVER with the beaten egg. Bake for 10 minutes, remove from the oven. The center of the puff pastry should puff up and turn golden brown.
Spread the marinara sauce, then mozzarella cheese, toppings, followed by dollops of pesto. Bake for another 10 minutes or until cheese is bubbly and melted. Cut into 9 equal squares and serve with chili pepper flakes.
Notes
A quick and easy alternative to traditional pizza that is great as an appetizer or light meal.