Preheat oven to 200°C.
Toss frozen vegetables with canola oil and spread evenly onto a sheet pan. Place into oven and cook until golden brown.
In a saute pan heat 1 tablespoon of butter and sweat the onion and celery. In another saucepan, heat the broth and milk. Add 2 more tablespoons of butter to the celery mix and cook out the water.
Add the flour and curry and cook for 1 to 2 minutes. Whisk in the hot milk mixture and cook until thickened. Add the parsley, salt and pepper. Toss the browned vegetables and the chicken.
Pour into a shallow baking pan, or a large terracotta pot base, lined with foil, and top with 6 to 8 circles of puff pastry. Place into the oven and cook until puff pastry has browned and the mixture is hot and bubbly, about 25 minutes.