Beef in Mushroom Sauce

1/2 cup finely chopped onion
2 cups frozen mixed vegetables, thawed
and drained
2 cloves garlic, minced

1 lb. lean ground beef

4 oz uncooked medium wide egg noodles

Sauce: 10 3/4 oz can mushroom soup
1 cup milk
8 oz can sliced mushrooms with liquid
2 tsp Dijon mustard

1/2 tsp each of dried thyme and marjoram
1/4 tsp each salt and pepper

1 cup coarsely shredded Gruyere cheese
or 1/2 cup each of Gruyere and Parmesan

Preheat oven to 350. 
Saute the vegetables in oil, butter or margerine in a deep
skillet until slightly softened - 3 to 5 minutes.
Add the meat and seasonings. Cook, stirring, until meat is no 
longer pink.
Mix in the soup and other Sauce ingredients. Bring to a simmer.
Stir in the noodles.
Spoon into an 11x9x2 baking dish.
Sprinkle with the cheese.
Bake, uncovered, 35 to 45 minutes, until bubbling and lightly browned.