Heat oven to 400°F and prepare two baking sheets using parchment paper, or coat with cooking spray.
Sprinkle flour on your work surface and roll out the pastry square as thinly as you can. With a pizza cutter or sharp knife, slice the puff pastry into small squares (about 4″ by 4″).
Place one-half of cheese and the salami, vegetables, spices, oil, and vinegar in a food processor. Pulse until finely chopped.
On half of the squares, sprinkle the second portion of sliced mozzarella, then place about 1-2 teaspoons of the mixture on top. Season with salt and pepper. Top with remaining pastry squares. Seal pastries carefully, pressing edges with a fork.
In a small bowl, beat 1 egg with a fork and brush pastries with egg wash or water for a secure seal.
Bake for about 13 minutes. (Check after 10 minutes, as oven temperatures vary slightly.) When your pastries are golden brown, remove them from the oven onto a glass plate.