1. Place the mushrooms in a bowl and add 2 1/2 cups of warm water. Allow to soak for 30 minutes.
2. Drain the mushrooms in a fine sieve, reserving the soaking liquid. Set the mushrooms aside.
3. In a saucepan, bring the chicken broth and the reserved mushroom liquid to a boil. Reduce the heat to a simmer.
4. Meanwhile, in a large heavy pot, melt 2 tablespoons of the butter in the oil over medium heat. Add the shallots and sauté until translucent. Add the rice and cook, stirring, until the rice is completely coated. Stir in the white wine. Cook, stirring, for 2 minutes, or until the rice begins to absorb the liquid.
5. Begin stirring in the hot broth, about 1/2 cup at a time, stirring constantly after each addition until it is absorbed. When half of the broth has been added, add the mushrooms and sun-dried tomatoes. Continue adding the remaining broth, stirring until absorbed.
6. Remove the pan from the heat and stir in the Parmesan and the remaining 2 tablespoons of the butter. Season with salt and pepper to taste. Serve the risotto with additional grated Parmesan.