Spinach Skillet Bake

I was trying to think of something to make with spinach and ground beef, so I typed those two ingredients into allrecipes.com and this is one that came up.  I put a ton of basil in it, and it was really good!

Ingredients:

1 lb ground beef
1 medium onion, chopped
1 10 oz pkg frozen chopped spinach
1 4 oz can mushroom stems & pieces, drained
1 tsp garlic salt
1 tsp dried basil
1/4 cup butter or margarine
1/4 cup flour
1/2 tsp salt
2 cups milk
1 cup shredded Monterey Jack or mozzarella cheese

In an ovenproof skillet, cook ground beef and onion over medium heat until no longer pink; drain.  Add the spinach, mushrooms, garlic salt and basil.  Cover and cook for 5 minutes.  In a saucepan, melt butter.  Stir in the flour and salt until smooth.  Gradually add milk.  Bring to a boil; cook and stir for 2 minutes or until thickened.  Pour over meat mixture; mix well.  Sprinkle with cheese.  Bake, uncovered at 350 degrees for 20-25 minutes or until heated through.