Heat olive oil in a large skillet over medium-high heat.
Add the chicken pieces and cook until browned on all sides, about 5-7 minutes. Remove chicken from skillet and set aside.
In the same skillet, add the diced onion and cook until softened, about 3-4 minutes.
Add minced garlic and cook for 1 minute until fragrant.
Reduce heat to medium and add butter to the skillet. Once melted, whisk in the flour and cook for 2 minutes to form a roux, stirring constantly.
Gradually whisk in the chicken broth and milk, ensuring no lumps remain.
Add dried thyme, salt, and black pepper. Bring the mixture to a simmer.
Add the egg noodles to the skillet and stir to combine.
Return the browned chicken pieces to the skillet, submerging them in the gravy.
Cover the skillet and cook for 10-12 minutes, stirring occasionally, until the noodles are tender and the chicken is cooked through.
Remove from heat and sprinkle chopped fresh parsley over the top before serving.