Instructions

Place 2 ounces rinsed dried porcini mushrooms in large bowl; cover with 4 cups boiling water and soak for 20 minutes. Drain mushrooms, reserving liquid. Using your hands, squeeze mushrooms over reserved liquid to release any remaining liquid and pat dry using paper towels. Set mushrooms and reserved liquid aside.
Heat 2 tablespoons extra-virgin olive oil in large Dutch oven over medium heat until shimmering. Add ½ pound thinly sliced mixed fresh mushrooms, half of prepared porcini mushrooms, ¼ teaspoon salt, and ¼ teaspoon pepper and cook until mushrooms start to brown, 6 to 8 minutes. Transfer mushrooms to large plate. Add remaining 1 tablespoon extra-virgin olive oil to now-empty Dutch oven and repeat with remaining ½ pound thinly sliced mixed fresh mushrooms, remaining half of prepared porcini mushrooms, ¼ teaspoon salt, and remaining ¼ teaspoon pepper.
Melt 2 tablespoons unsalted butter in now-empty Dutch oven. Add 1 finely chopped shallot and 2 minced garlic cloves and cook until fragrant, 1 to 2 minutes. Add 1½ cups orzo and 1 teaspoon dried thyme and cook 1 minute longer. Stir in ½ cup dry white wine, scraping up any browned bits. Cook until wine is absorbed, about 30 seconds. Add 2 cups chicken broth and 3 cups of reserved mushroom soaking liquid and bring to boil, then reduce to simmer. Simmer uncovered for 15 minutes, stirring occasionally, until liquid is absorbed.
Off heat, stir in ¾ cup grated Parmesan cheese, 3 tablespoons sour cream, remaining 1 teaspoon salt, and browned mushrooms. Season with salt and pepper to taste. Sprinkle with 2 tablespoons chopped chives. Serve.