Preheat the oven to 350°F and parboil 2 peeled potatoes for about 10 minutes. Once the potatoes have cooked, drain them and set them aside to cool. For the first casserole layer, butterfly both chicken breasts, place them on a piece of plastic wrap, and unfold them.
Place a second layer of plastic wrap on top of the chicken breasts and flatten them using a meat tenderizer.
Transfer 1 of the tenderized chicken breasts to the bottom of a 9 x 9 in casserole dish.
For the marinade, combine the tomato paste, ketchup, 3 tablespoons of olive oil, and chopped thyme in a small mixing bowl, then brush ½ of the marinade over the surface of the first layer of chicken breast.
Place 4 slices of Gouda cheese on top of the marinated chicken breast.
Chop the eggplant, zucchini, beefsteak tomatoes, and yellow bell pepper, then transfer them to the casserole dish. Season the vegetable layer with salt & pepper.
Cut the white bread into cubes and combine them with 3 tablespoons of olive oil and chopped rosemary. Stir everything together thoroughly and add a layer of bread cubes on top of the vegetable layer.
Place the second chicken breast on top of the layer of bread cubes.
Brush the remainder of the marinade over the second chicken breast.
Grate the parboiled potatoes directly on top of the second chicken breast layer and sprinkle grated parmesan on top.
Transfer the casserole dish to the oven and bake at 350°F for 40 minutes until the potato topping is crispy and golden brown.
