Add the diced tomatoes, beef broth, onion, carrots, celery, garlic, Italian seasoning, salt, and pepper to the slow cooker. Stir to mix well. Season the beef shanks generously with salt and pepper. Nestle the beef shanks into the tomato mixture in the slow cooker.
Cook HIGH 3-4 hours or LOW 6-8.
Season beef shanks generously with salt & pepper.
Turn on the Instant Pot and select sauté. Once hot add oil to the pot. Add the beef shanks and sear until lightly browned, 2-3 minutes on each side. You may have to do this in batches. Remove the beef from the pressure cooker and set aside.
Add the celery, onion, and carrots. You may need to add more oil. Cook 5-7 minutes or until the vegetables are soft. Add the garlic and cook and additional minute.
Turn off the pressure cooker. Pour the beef broth and de-glaze the bottom of the pressure cooker by scraping all the bits off with a wooden spoon. Stir in the Italian seasoning. Add the beef shanks back into the pressure cooker. Pour the diced tomatoes on top. Do not stir.
Close lid and seal valve. Set high pressure and cook for 35 minutes. When cooking time is complete, let the pressure naturally release the pressure for 15 minutes then manually any pressure.
