- Preheat oven to 400°F (200°C). Butter an 8-inch (2 L) square dish.
- In a large pot, bring broth to a boil. Add potato, carrot, parsnip and squash; simmer covered for about 10 min or until vegetables are tender.
- Stir in peas. Cook covered for 2 minutes.
- Reserving broth, drain and transfer vegetables to a large bowl along with chicken. Check to make sure you have 2 cups (500 mL) of broth left; if not add a bit more broth or milk.
- Melt butter in a large skillet set over medium heat. Add onion and garlic. Cook, stirring occasionally, for 3 minutes.
- Stir in thyme, mustard, basil, salt and pepper. Sprinkle with flour; cook, whisking, for 1 minute.
- Gradually whisk in milk and reserved broth. Bring to a boil and reduce heat. Whisk for 3 to 5 minutes or until smooth and thickened.
- Pour sauce over vegetable mixture; stir until well coated. Transfer to prepared dish.
- Place 1 sheet of phyllo on work surface; brush entire phyllo surface with butter (keep remaining phyllo covered with plastic wrap and a damp towel).
- Lay second sheet on top of first; brush with butter.
- Repeat with remaining 2 sheets of phyllo.
- Cut phyllo into 4 equal-sized rectangles. Crumple a rectangle slightly; place on 1/4 of filling, tucking edges on inside of dish. Repeat with remaining phyllo rectangles, on other 3 quarters, covering entire surface of filling.
- Bake for 20 min or until filling is hot and bubbling and phyllo is golden. Let stand for 10 min before serving.
Cooking tip: If phyllo is torn, don’t worry, you’ll never know after the sheets are stacked and crumpled for the topping.