Melt 2 tbsp. of butter in a 14-in. frying pan or 5-qt. saucepan over medium heat. Add leeks, mushrooms, 1 tsp. salt, and nutmeg; cook, stirring often, until vegetables are soft and beginning to brown, about 12 minutes. Using a slotted spoon, transfer vegetables to a bowl and set aside.
Bring a large pot of water to a boil. Add 3 tsp. salt and egg noodles. Cook until barely tender to the bite. Drain noodles and set aside, covered.
While noodles are cooking, melt remaining 3 tbsp. butter in the same pan. Sprinkle in flour and stir until mixture looks glossy and golden brown, about 3 minutes. Whisk in chicken broth and sherry and simmer until thickened, about 3 minutes. Remove from heat and whisk in half-and-half, parmesan, and remaining 1 tsp. salt. Reduce heat to low, return pan to heat, and stir in vegetable mixture, turkey, and parsley. Just before serving, stir in radicchio. Serve over cooked noodles and garnish with parsley.
Note: Nutritional analysis is per serving.