Warm the chicken broth in a small saucepan over low heat and keep it at a bare simmer.
Heat the olive oil in a large skillet over medium heat. Add the diced chicken breast, season with half of the salt and pepper, and cook until golden and cooked through. Remove the chicken and set aside.
In the same skillet, add the diced onion and sliced mushrooms. Sauté for 5-7 minutes until the mushrooms are browned and the onions are translucent.
Stir in the minced garlic and arborio rice, toasting the grains for 2 minutes until the edges of the rice appear slightly clear.
Add the warm broth to the rice one ladle at a time, stirring constantly. Wait for the liquid to be fully absorbed before adding the next ladle.
Continue this process for about 18-20 minutes until the rice is tender but still has a slight bite and a creamy consistency.
Fold the cooked chicken back into the skillet along with the parmesan cheese, fresh thyme, and the remaining salt and pepper.
Remove from heat and serve immediately while the risotto is at its peak creaminess.