Begin by peeling and chopping about 2 pounds of potatoes into equally sized chunks. Place them in a large pot of salted water and bring to a boil. Cook for approximately 25 minutes or until tender when pierced with a fork. Drain the potatoes and set them aside to cool slightly while you prepare the next steps.

In a large skillet over medium heat, add 6 slices of bacon. Cook until crispy, which should take around 8-10 minutes, flipping halfway through for even crispiness. Once done, remove the bacon from the skillet and set aside on a paper towel-lined plate, leaving the rendered fat in the skillet for added flavor.

Using the same skillet with the bacon fat, add 1 diced onion. Sauté over medium-low heat for about 8-10 minutes until the onions are soft and caramelized, stirring occasionally to avoid burning.

In a large mixing bowl, combine the cooled, cooked potatoes, 2 cloves of minced garlic, 1 cup of sour cream, 4 tablespoons of butter, ½ cup of milk, and ½ cup of cream. Using a hand mixer or potato masher, blend until smooth and creamy, ensuring there are no lumps. Season the mixture with salt to taste.

Bring a large pot of salted water to a boil and cook the lasagna noodles for about 5 minutes less than the package instructions recommend. Once they are slightly undercooked and pliable, drain the noodles and toss them with a drizzle of olive oil to prevent sticking as you assemble your Pierogi Lasagna.

In a 9x13-inch baking dish, spread a thin layer of the potato mixture on the bottom. Begin layering with lasagna noodles, followed by crumbled bacon, caramelized onions, and shredded cheddar cheese. Repeat these layers until you run out of ingredients, finishing with a layer of potato mixture, topped generously with cheese.

Preheat your oven to 350°F (175°C). Cover the baking dish with aluminum foil and bake for about 30 minutes. For an extra golden top, remove the foil during the last 10 minutes of baking.

Once baked, remove the Pierogi Lasagna from the oven and let it cool for about 10 minutes. This resting period ensures that the layers set properly, making it easier to cut and serve.

Before serving, sprinkle the reserved crispy bacon and freshly chopped scallions on top of your Pierogi Lasagna.