Preheat oven to 350 degrees F.
Heat olive oil in a large cast iron skillet over medium-high heat.
Once hot, add chicken breasts and sear on each side for 2-3 minutes, until golden brown but not cooked through.
Remove from the skillet and set aside.
Add 2 tablespoons of butter to skillet along with remaining olive oil over medium-high heat.
Add shallots and mushrooms, and cook for 8-10 minutes, until the mushrooms are cooked.
Add garlic and cook for one more minute. Remove from pan.
Add remaining butter to pan. Once melted, add arborio rice, stirring to mix with the butter, and toast for 1 minute.
Add wine and cook until it has mostly evaporated.
Add chicken broth and stir to combine.
Add mushroom and shallot mixture, stirring until combined, then top with chicken breasts.
Cover with aluminum foil or lid for the pan, and bake in preheated oven for 20 minutes.
Remove foil/lid and cook another 10-15 minutes, until rice has absorbed the liquid and chicken is cooked through.
Remove chicken from pan then add milk.
Start with ¼ cup and add more to reach your desired consistency.
Stir in Parmesan cheese, stirring until well combined.
Return chicken to skillet and serve sprinkled with fresh thyme.
Enjoy!