Preheat your oven to 375°F (190°C).
Caramelize the onions by slicing them thinly and cooking in olive oil over medium heat until golden.
Prepare the filling by mixing the caramelized onions, mozzarella, cream cheese, garlic powder, salt, and pepper in a bowl.
Flatten each chicken breast to about 1/2 inch thickness using a meat mallet.
Spoon the filling onto each chicken breast and roll tightly, securing with toothpicks if necessary.
Heat olive oil in a skillet over medium heat and sear each roll until golden brown on all sides.
Transfer the seared chicken rolls to a baking dish and bake for 25-30 minutes or until the chicken is cooked through.
Remove from the oven, let cool briefly, and garnish with fresh parsley before serving.
