Leeks -- In a small sauce pan on medium high heat, add the butter and melt. Then add the garlic, leeks and cook on medium (you don't want to brown them) for about 5 minutes until tender. Then add in the scallions and diced turkey and cook another minute. Don't forget to salt and pepper well.
Crust -- As the leeks saute, make your crust. Now I prefer to use a tart pan, but not everyone has one. You can make a rough or rustic tart and just lightly crimp the sides up around the tart which is fine. But you want something around 10-12" round. A pizza pan also works for this and you can also make this on a pizza stone. If making it on a pizza stone or a pizza pan I line with parchment paper, so it doesn't stick (not necessary, just something I liked to do). If using a tart pan, spray with non stick spray.
Unroll the pizza dough and roll on a floured surface into a circle. About 14-16", thin but you don't want it falling apart. Then in the tart pan, pat on the bottom and then pat up the sides. If using a pizza stone, pan, etc., don't crimp up the edges until you fill the crust with the fillings.
Potatoes -- To your leftover potatoes, add in the chives, egg, garlic, and 1/4 cup cheese. Mix the potatoes well and then spread the potato mixture on to the pizza dough.
Note: If using fresh homemade mashed potatoes vs leftovers, just make a basic recipe with butter and cream and then add in the chives, egg, garlic and cheese liked stated above.
Tart -- For the tart pan, fill the bottom of the pan. If using a pizza stone or pizza pan, spread the potatoes on the pizza dough leaving 2" around the edge so you can fold them over form a crust. Just don't fill it all the way to the edge.
Leeks and Turkey -- Spread the leeks, scallion, garlic and turkey mixture over the potato and top with the remaining cheese.
Bake -- In a 375 degree oven, bake for 20 minutes until golden brown. If using a pizza stone, don't forget to heat up the stone first. After the cheese is melted and the crust is golden brown, remove and let set just 5 minutes before serving.
Serving -- Cut in slices like a pizza and serve with a scoop of cranberry sauce on the top. Serve with balsamic green beans and a pumpkin parfait. Leftovers are great!