Begin by deboning the whole chicken, if not already done. Carefully remove the bones, ensuring you keep the skin intact. Rinse the chicken under cold water and pat it dry with paper towels.
In a small bowl, mix the olive oil, mustard, smoked paprika, turmeric, salt, and pepper. Rub this mixture all over the chicken, including the inside. Let it marinate for at least 30 minutes to absorb the flavors.
In a large skillet, heat a tablespoon of olive oil over medium heat. Add the finely chopped leeks and onions. Sauté until they are soft and fragrant, about 5-7 minutes. Remove from heat and let cool slightly.
On the flattened chicken, layer the sautéed leeks and onions evenly. Place the tomato slices on top and then scatter the cheese sticks over the vegetables.
Starting from one end, carefully roll the chicken tightly, keeping the filling inside. Secure the roll with kitchen twine or toothpicks to hold it in place.
Preheat your oven to 180°C (350°F). Place the stuffed chicken roll in a baking dish, cover it with aluminum foil, and bake for 45 minutes. Remove the foil and bake for an additional 15-20 minutes, or until the chicken is cooked through and the skin is golden brown.
Once cooked, remove the chicken roll from the oven and let it rest for about 10 minutes before slicing. This allows the juices to redistribute, ensuring a moist and flavorful roll. Slice and serve warm, enjoying the beautiful layers of leeks, tomatoes, and melted cheese.