Place the sliced mushrooms, diced onion, and minced garlic into the slow cooker.
Add the vegetable broth, Worcestershire sauce, dried thyme, paprika, salt, and black pepper. Stir everything together.
Cover and cook on low for 6 to 7 hours or on high for 3 to 4 hours until the mushrooms are soft.
Stir the sour cream into the mushroom mixture until the sauce turns smooth.
Cook the egg noodles in a large pot of boiling water according to the package directions, then drain.
Spoon the mushroom stroganoff over the cooked noodles and sprinkle with chopped parsley before serving.