Add the ham,the carrot, the corn, the lima beans, the broth, the water, and the thyme and simmer the stew, covered, for 10 to 12 minutes, or until the carrot is tender. While the stew is simmering, in a bowl whisk together the cornmeal, the flour, the baking powder, and the salt, add the Cheddar, and toss the mixture well. Stir in the milk until the dough is just combined.