Honeynut Squash (or any seasonal squash)
Dried mustard powder
Herbs: sage, rosemary or thyme (or a mix of all)
1) Scrub and trim the potatoes and get them into a pot of salted boiling water. While they are cooking:
2) Wash and thinly slice the leeks and carrots and get them started in a pan with olive oil. While they soften, cube the honeynut (no need to peel but feel free to if you prefer) and trim and quarter the radishes.
3) Add the squash & radishes to the pan and allow to cook and soften a bit (5-10 mins.) Season with rosemary and thyme and season to taste with salt & pepper. While they are cooking, lightly wipe the mushrooms with a damp paper towel to remove any dirt (note: mushrooms are like sponges so it's not best to rinse under the tap) then just quarter them and set them aside. Preheat the oven to 350F
4) After about 5 minutes, transfer the leeks, carrots, squash and radishes to your pie dish (it's ok if there's a little bit stuck to the bottom of the pan.) Then add a pad of butter and the mushrooms (this extra step of sauteing the mushrooms separately ensures they keep their shape and get a nice browning on them)
5) Then add the mushrooms to the pie dish. Add a little more butter to the skillet, and a couple spoonfuls of flour. Allow to cook for a couple mins, whisking to form a roux. Add some (about a cup, add slowly and adjust--you can always add more) vegetable stock and stir, then cook to thicken into a gravy. While that's cooking, drain the potatoes, add some butter and milk and mash. Add some dried mustard powder if you'd like. Adjust by adding more milk until you like the consistency of the potatoes.
6) Pour the gravy over the vegetables, and then spoon the mashed potatoes over the top. Using a fork create small peaks--these will catch and become cripsy in the oven. Sprinkle cheese (cheddar or Parmasan are great) if you'd like and pop the pie in the oven for about 25-30 mins or until the potatoes are crispy.