Melt the butter in a large pot over medium heat. Add the ground beef, diced onion, and minced garlic. Cook until the beef is browned and the onion is soft, breaking up the meat as it cooks.
Stir in the sliced mushrooms and cook for 3 to 4 minutes until they begin to release liquid.
Pour in the beef broth and add the dried thyme along with salt and black pepper. Bring the mixture to a boil.
Add the egg noodles and reduce the heat to a simmer. Cook for 8 to 10 minutes, stirring occasionally, until the noodles are tender.
Remove the pot from the heat and slowly stir in the heavy cream until the stew turns creamy and smooth.
Ladle into bowls and sprinkle with the chopped fresh parsley before serving.