Cover the bottom of the dish with chunks of turkey in a double layer. Pour the gravy over the turkey to cover it. Don't add too much gravy to this pie or, if you are using mashed potatoes, the layers may not stay distinct. It's better to serve extra gravy on the side if you have a lot of it.

Next add a layer of roasted carrots and parsnip or other leftover vegetables.

If you have leftover stuffing, add that next. It provides a very good insulating layer between the gravy and potatoes, helping to keep the layers distinct but if you don't have any, it's not a deal breaker for this versatile recipe.

Finally you can spread on the mashed potato layer. Run a fork lightly over the surface to create lines or a grid pattern to hold the melted butter, helping it brown better. If you want to be "fancy", transfer your mashed potato to a Ziploc bag and snip the corner off with a pair of sharp scissors and use the bag to pipe the mashed potato in little peaks or swirls all over the surface of the pie.

Finally, drizzle the top of the mashed potatoes with a few tablespoons of melted butter. Pop the pie into a 350 degree oven and bake until the top is golden and the gravy starts to bubble.

For the sliced potato top instead, use about 1 large potato per person. Peel and cut the potatoes into 1/4 inch slices. Par boil the sliced potatoes in lightly salted water for about 4 minutes.

Drain the potatoes and cool the slices on a cookie sheet until they are able to be handled.

Overlap the potatoes all over the surface of the cottage pie and brush them with melted butter before popping the baking dish into a pre-heated 350 degree oven until the top begins to brown, the potatoes are fork tender and the gravy beneath is bubbling, about 40-50 minutes depending upon the size of your casserole dish. Smaller individual serving dishes will only need 20-30 minutes, again depending upon the size.