Being in Pittsburgh has brought many pierogies into my life.  (I have heard pierogi used as the plural form as well, and I'm not really sure which is correct!)  And everyone has their own way of making them.  The traditional version in this area have potato and cheese filling and are cooked in butter.  I usually cook them with butter and onions, topped with sour cream.  Jake prefers Eastern European pierogies made with sauerkraut.  They're all good, really.  

This "lasagna" includes all of the above and makes the whole process a lot easier.  Premade noodles from the store help, but also you just layer it all together instead of making each pierogi individually.  Jake and I both loved the end product.  Of course, you can adapt it however you like with different cheeses, fillings, etc.  Just make sure that there is enough moisture so that the pasta and potatoes don't dry out.  And, of course, I love how you can use leftover holiday mashed potatoes (or any dinner, really) in a dish that is so dramatically different than the meal that they were originally served in.

Pierogi Lasagna

12 lasagna noodles (not the no bake kind) 4 Tbsp butter 4 Tbsp olive oil 1 large onion, diced 1/2 tsp salt 1/4 tsp pepper 1 clove garlic, diced 1 cup sauerkraut 4 cups prepared mashed potatoes - this is perfect for leftovers!  If yours were plain, mix in some Parmesan cheese, etc to add some flavor 3 cups sharp cheddar cheese (freshly shredded is best for melting)

Preheat the oven to 350 degrees.

Boil the lasagna noodles per package instructions and drain.  Separate and set aside.

Meanwhile, melt the butter with the olive oil over medium heat.  Add the onion, salt, and pepper and saute for about 5 minutes until it softens.  Add in the garlic and sauerkraut and cook for another 5 minutes.  You want the mixture to be very moist; add olive oil if necessary.

In a 9 by 13 inch baking dish, put a thin layer of the onion mixture on the bottom.  Layer 3 of the lasagna noodles in a layer on top, then 1/4 of the mashed potatoes, another layer of the onion mixture, and a layer of cheese.  Continue these layers three more times, making sure that the cheese is on top as the last layer.

Cover with aluminum foil and bake for 20 minutes.  Remove the foil and bake uncovered for another 20 minutes, or until it is bubbling and hot.  If you want to brown the top at the end, you can put it under the broiler for a minute.  Serve warm.

Source: Inspired by my coworker, Chris, who told me about something similar she makes for her family.