Season the steak with salt and pepper.
Heat up the oil in a pan over a medium heat, and brown the steak on both sides for 3-4 minutes.
Remove from the pan and transfer it to the slow cooker.
Peel and chop the onion, garlic, carrots and celery sticks.
In the same pan, fry the onions until soft adding more oil if necessary.
Add the chopped garlic, carrots and celery, give it a good stir, then add the canned tomatoes and beef broth.
Transfer everything to the slow cooker and leave to cook on high for 5-6 hours or on low for 8-10 hours until the beef is tender and the sauce has thicken.
Use 2 forks to shred the beef if there are big chunks, although at this stage the beef is very tender and fall apart easily.
Add the parmesan, season to taste, and garnish with chopped parsely.
Serve with any pasta of your choice.