Preheat oven to 400 °F (200 °C) and line a baking sheet with parchment paper (not wax paper). Arrange mozzarella cheese slices on parchment paper with enough space in between each slice so they won't melt into each other.
Place baking sheet with the cheese slices into the preheated oven and bake for 5 to 7 minutes or until the edges of cheese are browning. Remove from oven and let the cheese cool for 3 to 4 minutes to firm but not completely harden.*Leave the oven on, as these will return to the oven later.*
In a small mixing bowl combine: tomato paste, Italian seasonings, and oregano leaves. Mix to combine.
Add 1 teaspoon of tomato paste mixture to the center of each cheese slice and add a pepperoni slice and a couple of string cheese slices on top.
Fold one corner of cheese over to the opposite corner pressing down gently with fingers to make a triangle shape and so the turnover stays folded over but it won’t seal at the edges as they only need to stay folded over because the edges will seal in the oven heat when returned to the oven.
Once all are folded over, return to the 400 °F oven and bake for 2 to 3 more minutes or until edges of the turnovers have melted together to seal.
Remove from oven and let cool just until the cheese shell is firm enough to pick up the turnover and have it keep its shape without bending.
Sprinkle parmesan cheese over the top of the turnovers and serve.
*all nutritional data are estimates based on the products I used*