Preheat oven to 350˚F.

Add a couple tablespoons of oil to a pan/skillet and heat over a medium heat. Add onions and mushrooms, seasoning with salt and pepper to taste. After about 7 to 8 minutes add garlic in and cook for a couple more minutes, until onions are softened.

In a large bowl add Alfredo sauce, 3/4 of the bacon, chicken, Italian seasoning and sauteed onions and mushrooms. Stir to combine.

Place pierogies into a 9x13 casserole dish. Pour chicken mixture over the top, cover in cheese and remaining bacon.

Place in the oven and bake for 30 minutes.