Step #1 Make the mushroom ragout: In a large deep skillet cook the onion, garlic, until the onion is softened, stirring, stirring, & rosemary in oil over moderate heat, add mushrooms & salt to taste, & cook the mixture over moderately-high heat, for 10 mins, or until the liquid the mushrooms give off is evaporated.
Step #2 stir in the the tomato paste & wine & boil the mixture until most of the liquid is evaporated.
Step #3 In a small bowl stir the cornstarch in the stock, add it & Worcestershire sauce to the mushroom mixture & bring ragout to a boil, stirring.
Step #4 Simmer ragout for 2 mins & Spice up it with salt & pepper.
Step #5 In a large heavy saucepan bring the water with oil to a boil & add 1 c of the cornmeal, a little at a time, stirring constantly.
Step #6 Reduce the heat to low, add the remaining 1 c cornmeal in a slow stream, stirring constantly, & bring the mixture to a boil.
Step #7 Remove the pan from the heat & stir in the the butter, 3/4 c of the Parmesan, parsley, & salt & pepper to taste.
Step #8 Spread one third of the polenta evenly in a buttered 13- by 9-inch baking dish and chill the polenta sheet for 20 mins, or until it is firm.
Step #9 While the polenta sheet is chilling, working quickly, spread half the remaining polenta in a buttered 3-quart shallow baking dish, top it with half the mushroom ragout, & top the ragout with the mozzarella.
Step #10 Spread the remaining polenta quickly over the mozzarella & top it with the remaining ragout.
Step #11 Invert the chilled polenta sheet onto a work surface & with 1 or more star shaped cutters, cut out as many stars as possible.
Step #12 Arrange stars decoratively on the ragout & Sprinkle top them with the remaining 1/3 c Parmesan.
Step #13 The layered polenta may be prepared up to this point 2 days in advance & kept covered & chilled.
Step #14 Preheat the oven to 400F degrees.
Step #15 Bake the layered polenta in the upper third of the oven for 30 to 40 mins, or until the polenta stars are golden.