1. Preheat oven to 350°.
2. Melt butter in a large nonstick skillet over medium-high heat. Add mushrooms to pan, and sauté 2 minutes or until lightly browned. Stir in garlic; sauté 30 seconds. Add wine; cook 2 minutes. Add parsley, thyme, and 1/4 teaspoon pepper. Cover, reduce heat, and simmer 10 minutes. Uncover and cook 6 minutes or until liquid almost evaporates. Remove from heat; discard thyme. Add cream cheese, stirring until cheese melts. Remove mushroom mixture from pan. Wipe pan clean with paper towels.
3. Heat pan over medium-high heat. Coat pan with cooking spray. Add onion; saute for 5 minutes, stirring frequently. Reduce heat to medium; continue cooking for 15 minutes or until deep golden brown, stirring frequently. Set aside.
4. Coat a 6-cup baking dish with cooking spray. Arrange potato slices in dish, and top with spinach. Sprinkle 1/4 teaspoon salt and 1/4 teaspoon black pepper evenly over spinach. Spoon the mushroom mixture over black pepper, and arrange turnip slices over mushroom mixture. Top with caramelized onions; sprinkle with remaining 1/4 teaspoon salt, remaining 1/4 teaspoon black pepper, and tarragon. Pour whipping cream over tarragon, and sprinkle evenly with Gruyère cheese. Cover and bake at 350° for 40 minutes. Uncover and bake an additional 20 minutes or until vegetables are tender and cheese begins to brown.
MyRecipes is working with Let's Move!, the Partnership for a Healthier America, and USDA's MyPlate to give anyone looking for healthier options access to a trove of recipes that will help them create healthy, tasty plates. For more information about creating a healthy plate, visit www.choosemyplate.gov.