Place the ground beef in a skillet, and saute until completely browned.
Cook the pasta to your liking and drain well.
Remove the ground beef, set aside, and discard the excess grease.
To the same skillet, add the butter, mushrooms, onions, and peppers. Saute until the vegetables have softened.
Reduce the heat to medium-low, and stir in the Worcestershire sauce and French onion soup.
Stir the cornstarch with a bit of water, and add it to the skillet. Simmer until the sauce thickens.
Mix in the ground beef and pasta, and stir to combine.
Place the cheese into the skillet, cover it with a lid, and allow the cheese to melt before serving.
