Pour the milk and soup stock into a big pot and heat on the stove over medium heat, until boiling. When the pot reaches a rolling boil, add the cornmeal, whisking it in a little at a time and avoiding lumps.
Lower the heat and continue to stir regularly on simmer, until the mixture thickens. This should take about 5-7 minutes.
Take it off the stove and add the Parmesan cheese.
You can serve the polenta as-is, with sauce on top (and some cooked veggies if your kids will eat them!) or put it into a greased 9-inch baking dish, spread the sauce on top, and bake for 10 minutes, until the sauce is bubbly.