Heat the oil in a heavy large skillet over medium-high heat. Add the chicken, season with salt and pepper, and cook until the juices evaporate and the chicken is golden, about 10 minutes. Add the shallots and garlic and saute until tender, about 2 minutes. Add the wine and stir to scrape up any brown bits on the bottom of the skillet. Add the rosemary and mix well. Add the Marinara Sauce and bring to a simmer. Reduce the heat to medium-low and simmer gently until the flavors blend, about 10 minutes.
Meanwhile, bring a large pot of salted water to a boil. Add the linguine and cook until al dente, stirring occasionally, about 8 minutes. Drain, reserving 1 cup of cooking liquid. Add the linguine to the ragu and toss to coat, adding some reserved cooking liquid to moisten. Transfer the pasta to a large serving bowl. Sprinkle with Parmesan and serve.
In a large casserole pot, heat the oil over a medium-high flame. Add the onions and garlic and saute until the onions are translucent, about 10 minutes. Add the celery, carrots, and 1/2 teaspoon each of salt and pepper. Saute until all the vegetables are soft, about 10 minutes. Add the tomatoes and bay leaves, and simmer uncovered over low heat until the sauce thickens, about 1 hour. Remove and discard the bay leaf. Season the sauce with more salt and pepper, to taste.
The sauce can be made 1 day ahead. Cool, then cover and refrigerate. Rewarm over medium heat before using.)
Recipe courtesy Giada De Laurentiis