Add the chicken thighs to the slow cooker. Layer the sliced mushrooms, diced onion, and minced garlic on top.
Pour in the chicken broth and sprinkle with thyme, salt, and black pepper. Cover and cook on low for 6 hours.
Stir in the cubed cream cheese until it melts into the sauce and creates a creamy texture. Continue cooking for 30 more minutes on low.
While the sauce finishes, cook the egg noodles in a large pot of boiling water according to package directions. Drain well.
Shred or slice the chicken directly in the slow cooker and stir it into the mushroom sauce. Spoon the mixture over the cooked egg noodles and top with fresh parsley.