Add the seared beef, stock, wine, tomato paste, parsley, paprika, garlic powder, mushrooms, onions and a good pinch of salt and toss. Set slow cooker to high, if necessary. Skim fat from surface. … Cook on high for 4 hours or low for 6 to 8 hours. Bring broth mixture to a boil, then transfer to slow cooker. Add beef and white mushrooms to slow cooker, cover and cook on high until meat is tender, 6 to 7 hours (or cook on low for 9 to 10 hours).