1. Combine flour, cheese, thyme and salt; cut in butter until crumbly. Add water, tossing until dough holds together when pressed. Shape into a disk; chill 1 hour
2. Melt butter in a large saucepan over medium-high heat. Add the carrots, celery and onion; saute until softened, 5-7 minutes. Add mushrooms; cook 3 minutes. Add Swiss chard and garlic; cook until wilted, 2-3 minutes. Whisk broth, flour, salt and pepper; slowly pour over vegetables, stirring constantly.
Cook until thickened, about 3 minutes. Stir in chicken and oregano.
3. Preheat oven to 400°. On a floured sheet of parchment paper, roll dough into a 12-in. circle. Transfer to a baking sheet. Spoon filling over pastry to within 2 in. of edge. Fold pastry edge over the filling, pleating as you go, leaving center uncovered. Bake on a lower oven rack until crust is golden brown and filling is bubbly, 30-35 minutes. Cool 15 minutes before slicing. Sprinkle with parsley.
Per serving: 342 cal., 21g fat (12g sat. fat), 81mg chol., 594mg sod., 22g carb. (2g sugars, 2g fiber), 16g pro.