Heat the olive oil in a large skillet; when hot add in the onion and garlic and saute until the onion is translucent being careful not to brown the garlic too much. Add in the ham pieces and the kale and saute for 2-3 minutes then dd the chicken stock and the tomatoes. Stir to combine. Season with the crushed red pepper, salt and black pepper to taste. Cook for about 7-10 minutes until the kale has wilted somewhat and is tender.