Pre-heat oven to 350 degrees and spray a 9 x 13 baking pan with cooking spray.
Cook pasta according to package directions and set aside.
Heat butter in a large skillet over medium heat until melted. Stir in onion, celery and 1 teaspoon of the salt. Cook until softened, 3-4 minutes before adding garlic and mushrooms. Continue cooking until mushrooms are soft, 3-4 additional minutes.
Sprinkle flour into the pan and stir for 30-60 seconds or until flour is absorbed into the pan. Pour in chicken broth and bring to a boil. Reduce heat to low and simmer until sauce thickens, 7-9 minutes.
In a large bowl, toss together cooked pasta with diced chicken, plain yogurt, remaining 1 teaspoon salt, half of the cheese (1 cup), lemon juice and Worcestershire sauce and pepper. Add in reduced mushroom sauce to the bowl and stir again.
Pour pasta mixture into the prepared baking dish and spread in an even layer.
In a small bowl, mix together remaining 1 cup cheese with panko and olive oil. Sprinkle mixture evenly on top of the casserole.
Bake until golden brown and bubbly, 45-50 minutes. Let rest 5-10 minutes before serving to let the casserole settle.