How to Make It
Preheat the oven to 425°. Season the chicken breast with sea salt and freshly ground pepper. In a small pan, heat the extra-virgin olive oil over medium high heat. Add the chicken and cook for 1 minute. Turn the chicken, reduce the heat, cover and cook for 8 minutes. Remove from the heat and leave covered for 10 minutes, then shred the chicken with 2 forks.
Meanwhile, arrange the bacon on a baking sheet and bake for 10 to 12 minutes, until quite crispy. Remove from the oven, let cool, then crumble it.
In an 8-by-10-inch casserole dish, arrange the pierogies and top them with an even layer of shredded chicken, bacon, onion and cheddar cheese. Bake for 15 to 20 minutes, until the pierogies are heated through. Serve with sour cream and sliced green onions.