Preheat the oven to 400 degrees Fahrenheit. Heat a tablespoon of olive oil in a large casserole dish or Dutch oven. Add the ground turkey, garlic powder, salt, pepper and oregano. Stir well to combine and cook the turkey through until browned all over.
Remove the dish from the heat. Drizzle the passata (tomato sauce) evenly over the cooked meat. Scatter the mozzarella evenly over the sauce layer.
Roughly tear the prosciutto and thinly slice the olives. Arrange the prosciutto over the mozzarella. Scatter the olives over the surface.
Transfer to the oven to bake for 10-12 minutes or until piping hot through, the prosciutto is crisp and the cheese is melted and bubbling. Scatter over the fresh arugula. Drizzle over the remaining olive oil to serve.