In a large pot or deep skillet, add the sliced mushrooms and cook over medium heat until softened and lightly browned. (You can add a tiny splash of oil if needed.)
Stir in the cooked ground beef and mix well.
Add the cream of mushroom soup and beef stock, stirring until smooth and combined.
Bring the mixture to a gentle simmer.
Add the egg noodles directly into the pot and stir to coat.
Cover and cook for 8–10 minutes, stirring occasionally, until the noodles are tender and have absorbed the sauce.
If the mixture gets too thick, add a splash of extra stock to loosen it up.
Serve hot and enjoy that creamy, cozy goodness.