Chicken Potpie -- Light Version

2 tablespoons butter
2 tablespoons olive oil
3 cups diced red potato (about 1 pound)
2 cups diced onion
2 cups sliced mushrooms (about 8 ounces)
1 cup diced celery
1 cup diced carrot
1/4 cup chopped fresh parsley
2 teaspoons chopped fresh thyme
2 1/2 tablespoons all-purpose flour
3 cups fat-free milk
1/2 cup fat-free, less-sodium chicken broth
2 cups chopped cooked chicken breast (about 12 ounces)
1 cup frozen green peas
1 teaspoon salt
1/2 teaspoon freshly ground black pepper
6 (14 x 9-inch) sheets frozen phyllo dough, thawed
Cooking spray

Preheat oven to 375°.
Melt butter in a large saucepan over medium-high heat; add oil. Add potatoes and next 6 ingredients (through thyme), and sauté for 5 minutes. Reduce heat to low; sprinkle flour over vegetables. Cook for 5 minutes, stirring frequently. Stir in milk and broth. Increase heat to medium-high; bring to a boil. Reduce heat, and simmer 5 minutes or until thickened. Add chicken, peas, salt, and pepper.
Spoon mixture into a 2-quart baking dish. Place 1 phyllo sheet on a large cutting board or work surface (cover remaining dough to keep from drying); lightly spray with cooking spray. Repeat layers with cooking spray and remaining phyllo. Place phyllo layers loosely on top of mixture in dish. Place dish on a baking sheet. Bake at 375° for 20 minutes or until top is golden. Makes 6 servings.