In a pot over medium heat, brown the ground beef, breaking it up into smaller pieces. Add the onion and mushrooms; season with salt and pepper. Cook until the vegetable start to soften. Mix in the flour and cook for 2 minutes.
Add the broth and thyme and bring to a boil over high heat. Once boiling, turn down to a simmer for about 20 minutes.
Remove the thyme sprigs, serve over noodles. Garnish with parsley.