Dice the chicken breast into small, bite-sized pieces and season with half of the salt and pepper.
Heat the olive oil in a wide skillet over medium heat and sauté the chicken until golden and cooked through, then remove from the pan and set aside.
In the same skillet, add the diced onion and sliced mushrooms, sautéing until the onions are translucent and the mushrooms have released their moisture.
Stir in the minced garlic and arborio rice, toasting the grains for about 60 seconds until the edges of the rice appear translucent.
Begin adding the warm bone broth 1/4 cup at a time, stirring frequently and allowing the liquid to be fully absorbed before adding the next ladle.
Once the rice is tender and the mixture is creamy, fold in the cooked chicken, remaining salt, pepper, and fresh thyme.
Stir in the grated parmesan cheese until melted and serve immediately while hot.