Combine the milk, broth, cornmeal, and salt in a medium saucepan over high heat.
When the mixture comes to a light boil, turn the heat to medium low, and simmer for 15 minutes, or until the liquid has been almost completely absorbed by the cornmeal. Whisk every few minutes so it doesn't stick to the bottom of the pot.
Add more liquid if necessary to keep the polenta from becoming overly thick. Sprinkle with Parmesan cheese and serve.