In a large saucepan, add the diced potatoes and cover with water. Bring to a boil over medium heat and cook until the potatoes are fork-tender, approximately 10 minutes. Drain the potatoes and set aside.
In a separate pan, heat the olive oil over medium heat. Add the chopped onion and minced garlic, and sauté until the onion becomes translucent and fragrant, about 5 minutes.
Add the cooked potatoes to the pan with onions and garlic. Sprinkle paprika, dried oregano, salt, and pepper over the potatoes. Stir well to evenly coat the potatoes with the spices. Cook for an additional 2-3 minutes, allowing the flavours to meld together. Remove from heat and set aside.
Heat a large non-stick skillet over medium heat. Place one flour tortilla in the skillet and sprinkle a quarter of the shredded mozzarella cheese evenly over the tortilla.
Spread a quarter of the potato mixture over half of the tortilla, leaving a small border around the edges. Fold the tortilla in half, covering the filling, and press down gently with a spatula.
Cook the quesadilla for about 2-3 minutes on each side, or until golden brown and crispy. Remove from the skillet and transfer to a cutting board. Repeat the process with the remaining tortillas and filling.
Allow the quesadillas to cool for a minute or two before cutting them into wedges. Serve warm, garnished with fresh cilantro leaves if desired.