In a large saucepan, cook bacon until almost crisp. Remove the bacon and take out all but 1 tbsp of the fat. Add the onions and cook until softened but not browned. Transfer the onion to a bowl. To the pan add the water, broth and sage and bring to a boil. Stirring constantly, add the cornmeal, a little at a time. Cook over low heat, stirring almost constantly, until it is thick and pulls away from the sides of the pan, 20-25 minutes. Stir in the butter, 2 tbsp of the Parmesan and half the onions. Spread in a 3 cup gratin dish. Mix the bacon into the remaining onion mixture and spread on top of the polenta. Sprinkle on the remaining Parmesan and bake in the middle of a preheated 400 oven until the cheese is melted and just starting to brown. This serves 2 as a main dish, 4 as a side dish. Can be doubled or tripled and can be made and assembled earlier in the day and baked when ready to serve.