Cook the large shell pasta according to the directions on the bag and drain (do not rinse).
Add the bacon to a cast iron skillet, cook until crisp and remove from the pan.
Crumble the bacon into small bits.
Add the ground beef to a large cast iron skillet (this browns very well) and brown until a deep brown crust appears before breaking the beef apart.
Stir the ground beef and brown until a deep crust appears on about 50 or so percent of the beef.
Remove the beef (you can leave the fat) and add the onions.
Let brown for 1 minute before stirring, then let brown for another 1 minute before stirring again.
Add the beef back into the pan.
In a small cup mix the beef broth and the cornstarch until it is dissolved.
Add the ketchup, mustard, beef broth mixture, salt, and black pepper into the pan.
Cook until the mixture is only slightly liquidy (about 75% of the mixture is above liquid), 3-5 minutes.
Add the pasta back to the pan and mix together gently.
Add the bacon crumbles back into the pan.
Turn off the heat, add in the cheddar cheese and stir until melted.