Step 1 Mix polenta, flour, and a pinch of salt together in a bowl. Add table spread and rub in until mix resembles breadcrumbs. Add egg, and 1 teaspoon ice-cold water at a time to bind. Turn onto a floured surface and knead for a few minutes. Wrap and then chill for 30 minutes.
Step 2 Meanwhile, preheat oven to 180°C and prepare the pie filling. Lightly grease a 6-cup capacity pie dish. Place a frying pan over medium–high heat and spray with oil. Cook chicken for 5 minutes, in batches, until browned and cooked through. Cover and set aside.
Step 3 Respray pan with a little oil and cook onion for a few minutes, until softened. Add carrots, cook for 2–3 minutes. Add mushrooms and tarragon and cook for 2–3 more minutes. Place into pie dish with chicken and passata.
Step 3 On a lightly floured surface large enough to fit top of pie, roll out pastry. Cover pie dish with pastry, seal and trim edges. Prick surface several times with a sharp knife. Cook for 25–30 minutes, or until pastry is golden.
Step 4 Meanwhile, steam green vegies for 2–3 minutes until tender-crisp. Serve with pie.