Heat half the oil in a cast-iron skillet. Add the onion, peppers, salt, and pepper, and cook for 5 minutes. Add tomatoes with juices, breaking them up with a spoon. Cook for 3 minutes. Add paprika and stir well. Remove from the heat and stir in the chicken broth.
Heat the remaining oil in a separate skillet. Season the veal shanks with salt and pepper. Brown them on both sides. Remove the shanks from the skillet, add the wine, and scrape down browned bits. Simmer for 30 seconds.
Add the shanks into the skillet with onions, peppers, and tomatoes. Add wine a stir gently.
Preheat oven to 180C/350F.
Cover the shanks with aluminum foil. Braise the shanks for 2 hours or until very tender. Once cooked, remove the shanks onto a plate and keep them warm.
Whisk sour cream with flour and some of the cooking liquid. Pour the liquid back into the skillet with the remaining liquid, then place over medium heat. Simmer the sauce for 5 minutes, or until it thickens.
Add the shanks back to the skillet and simmer until heated through. Serve immediately.