Cook onion in part of the stock from the chicken. Drain and place onion in a bowl. Add ham and combine. Add chicken, milk, parsley and egg slightly beaten. Season with salt and pepper. Pour over prepared crust.
Bake in oven 350°F (180°C) for 20 to 25 minutes approximately or until cooked.Cool for 15 minutes before inverting quiche onto platter.
Combine flour, salt, oil and milk. Knead dough until all ingredients come together.Let dough stand covered for 30 minutes.Place dough on a lightly floured surface and roll out. Line a tart pan and trim edges.