Heat a large skillet over medium heat. Add the bacon strips and cook until golden brown, 6-8 minutes. Remove to a paper towel-lined plate and leave the grease in the skillet. Add the onion to the skillet and cook for 3-4 minutes, until slightly softened. Remove with a slotted spoon to a paper towel-lined plate. Meanwhile, cut the bagels into chunks, about 1-inch wide. In a large bowl, whisk together the eggs, half and half, kosher salt, black and cayenne pepper, parmesan cheese and parsley. Grease a 9-by-13-inch baking dish with butter or nonstick spray.  Place ½ of the bagel pieces into the dish. Crumble the bacon and sprinkle ½ of it over the bagels. Pour ½ of the egg mixture all over. Place all of the cooked onions evenly over top. Slice the block of cream cheese into 12 pieces and place the slices evenly over top of the bagel mixture. Repeat with a second layer of bagels, bacon and egg mixture. Cover with foil and refrigerate for 8 hours, or overnight. Preheat the oven to 350 degrees. Remove the casserole from the refrigerator and let sit at room temperature for 30 minutes. Bake for 50 minutes. Remove the foil and bake another 25-30 minutes until the top is golden brown, the center is hot, and the egg mixture is set. Let cool 15 minutes, then top with fresh dill. Serve immediately.