Cheesesteak Mac and Cheese

1 lb tri-tip beef or tender steak sliced thin
1 cup diced white onion
1-2 tablespoons oil
1 tablespoon butter
2 tablespoon flour
1 teaspoon beef flavor beef bouillion
2 cups milk
2 cups shredded cheese (mild cheese like; provolone mozzarella, Monterey Jack I used a combination of Jacka and mozzarella
8 oz pasta cooked according to package directions with salt
salt and pepper to taste

In a large skillet on high saute beef with onion in oil, just until beef is cooked to 135°.
Add in the flour and beef bouillion.
Then slowly pour in the milk as you stir and blend it into a sauce.
Stir in cheese.
Add pasta.
Add salt and pepper to taste.

You can use a whole pound of cooked pasta, just add another 1/2-1 cup milk so there is enough sauce to coat the pasta nicely.