Heat olive oil in a large skillet over medium-high heat.
Add the chicken pieces to the skillet and season with salt and black pepper. Cook for 5-6 minutes, stirring occasionally, until the chicken is browned and cooked through. Remove chicken from skillet and set aside.
In the same skillet, add the diced onion and cook for 3 minutes until softened.
Add the minced garlic and sliced mushrooms to the skillet. Cook for 5 minutes until mushrooms are tender and release their moisture.
Pour in the chicken broth and milk, stirring to combine.
Add the egg noodles, dried thyme, and dried parsley to the skillet. Stir well to submerge the noodles in the liquid.
Bring the mixture to a boil, then reduce heat to medium-low. Cover and simmer for 10-12 minutes, stirring occasionally, until noodles are tender and most of the liquid is absorbed.
Return the cooked chicken to the skillet and stir in the shredded cheddar cheese until melted and combined.
Season with additional salt and black pepper to taste.
Remove from heat and let the casserole sit for 2 minutes before serving.