Start by making shallow cuts on the chicken breasts using the oven rack as a guide.
In a large bowl, add the olive oil, the soy sauce, the brown sugar, the dried rosemary, the oregano, the salt, a pinch of black pepper and grate the cloves of garlic.
Add the chicken breasts and mix well to combine.
Cover the bowl with plastic wrap and let them marinate for 30 minutes.
Next, cut the onions into thin strips and set aside.
Cut the tomatoes into round slices, the mushrooms into strips and set aside.
In a medium baking dish, add all the onions we cut earlier, lining the entire bottom, and cover them with the mushrooms.
Add the tomato slices and finally add the seasoned chicken.
Take it to a preheated oven at 180° C (350° F) and bake for 40 minutes.
After this time has passed, add the grated mozzarella cheese on top of the chicken breasts.
Put everything back in the oven and bake until the cheese melts.
Serve.