1) In a medium saucepan over high heat, bring the chicken stock and the water to a boil. While whisking, slowly pour the polenta into the hot liquid. Stir in the salt. Lower the heat and simmer, stirring frequently, until the cornmeal is creamy and no longer grainy, about 30 minutes.
2) Remove the pan from the heat and stir the cheese and butter into the polenta. Serve at once.