Preheat the oven to 200°C. Peel and chop the potatoes into mediums size chunks. Boil the potatoes in water for 15-20 minutes until soft. Drain the potatoes, add the milk and butter, and mash.
Roughly slice the leeks and mushrooms. Mince the garlic. Remove the skin of the chicken breast and dice into cubes. Heat oil in a pan on medium heat. Add garlic and chicken and continue to cook until chicken is cooked through. Add the leeks and mushrooms until wilted and soft. Add mustard and Worcester sauce, salt and pepper to taste and set aside
Mix the milk and cornflour together. Slowly add milk-cornflour mixture to heated milk and stir constantly until thickened. Add thickened milk to leek, mushroom and chicken mixture. Set to the side. Pour chicken mixture into a casserole dish. Top with mashed potato and sprinkle with grated cheese, salt and pepper. Bake pie for 20 minutes
With ten minutes left to cook the pie, add oil to a medium pan and add minced garlic. Once fragrant add spinach or silverbeet. Add a small knob of butter, salt, pepper and a pinch of nutmeg at the end.
Once cooked let the pie cool for a couple of minutes. Add parsley to the top, and then dish out the pie and greens into bowls.
