Heat a stovetop-safe skillet over medium-low heat, or turn your pot to sauté.
Dry your beef well with a paper towel, and season it with salt and pepper. Set it aside at room temperature.
Cook your bacon in the heated skillet or pot.
When the bacon is done, use a slotted spoon to scoop it on to a plate and set aside.
If there is a lot of grease in the pot, drain most of it. Leave a little bit of the grease to brown the beef in.
Brown your beef in the bacon grease until browned on all sides, then set it aside on a plate.
Add your onions and mushrooms to the pan. If the pan is dry you can add back a bit of the bacon grease or a swirl of olive oil.
Cook the onions and mushrooms until they're nice and soft and the mushrooms are brown.
Stir in the mustard and the bread crumbs. Keep stirring it for about two minutes.
Add your beef back to the pot with the tomatoes (with the juices), bacon, and beef broth. If you prepared this in a separate pot, carefully pour it into your slow cooker.
Give it all a good stir and cover the pot.
Cook your stew on low for 8 hours.
Serve over freshly made dumplings, gnocchi, or mashed potatoes.