* Pancetta is Italian unsmoked bacon cured in salt and is available at most Italian markets and some specialty food stores. FOR FILLING: Combine first 3 ingredients (30 oz. ricotta, 10 oz. spinach, prepared as instructed, and 1/2 cup Parmesan) in large bowl. Season with salt and pepper. Add eggs and mix well. (Can be prepared 1 day ahead. Cover and chill.) always find a deeper dish easier toh (I always find a deeper dish easier (I always find a deeper dish easier to with salt and pepper, and cook l juices evaporate, stirring, frequently, about 12 minutes. ASSEMBLY: Cook noodles in large pot of boiling salted water until just tender but still firm to bite, stirring occasionally. Drain. Rinse under cold water to cool; drain. Oil 13x9x2-inch baking dish (I always find a deeper dish easier to deal with when making lasagna; 3-inches deep is MUCH better). Spread 1 cup Tomato, Porcini and Pancetta Sauce over bottom of dish. Arrange 3 to 4 noodles over, trimming to fit as necessary. Spread half of ricotta filling over. Spoon 1 cup sauce over. Sprinkle with 1 cup Fontina and 1/4 cup Parmesan cheese. Top with 3 to 4 noodles, trimming to fit. Spread remaining ricotta filling over noodles. Spoon 1 cup sauce over. Sprinkle with 1 cup Fontina and 1/4 cup Parmesan. Reserve 1/2 cup sauteed mushrooms for garnish. Spread remaining mushrooms over cheese. Arrange remaining noodles over. Spread remaining sauce over noodles. Sprinkle remaining Fontina and 1/4 cup Parmesan over. Cover with foil. (Can be prepared 1 day ahead. Refrigerate lasagna and reserved 1/2 cup mushrooms separately. Let lasagna stand 2 hours at room temperature before continuing.) Preheat oven to 350F. Bake covered lasagna 30 minutes. Uncover and continue baking until bubbling and cheese melts, about 20 minutes. Arrange reserved 1 cup mushrooms, tomato and 2 teaspoons rosemary over. Let stand 10 minutes. Cut into squares.