Heat the oil in a large pan and cook the onion and garlic for 3-4 minutes.

Add the beef and cook over high heat for 3 minutes, until browned all over. Add the paprika and stir well, then add the tomatoes, tomato paste, bell pepper, and mushrooms. Cook for 2 minutes, stirring frequently.

Pour in the beef stock. Bring to a boil, then reduce the heat. Cover and simmer for 11/2-2 hours, until the meat is tender.

Blend the cornstarch with the water, then add to the pan, stirring until thickened and smooth. Cook 1 minute, then season to taste with salt and pepper.

Transfer the beef goulash to a warmed serving dish, garnish with chopped fresh parsley, and serve with rice.