Heat the olive oil in a large frying pan over medium heat. Add the chicken pieces and cook until browned on all sides. Remove the chicken from the pan and transfer to a lasagne style baking dish.
In the same pan, add the onion and garlic. Cook for 7-8 minutes until the onion has softened.
Add the carrots, celery and cauliflower to the pan. Cook for about 5 minutes, or until the vegetables start to soften.
Stir in the peas, dried thyme, dried oregano and season with salt and black pepper. Cook for another 2 minutes.
Pour in the chicken stock and cream. Stir everything together and let it simmer for 5 minutes.
Transfer the contents of the frying pan to the baking dish.
In a small bowl, combine the panko breadcrumbs, Parmesan cheese, melted butter, garlic powder, and salt. Mix well.
Sprinkle the breadcrumb mixture evenly over the chicken and vegetables in the baking dish.
Bake for 25-30 minutes, covering with foil if the top browns too quickly.
Remove the casserole from the oven and let it cool for a few minutes before serving.