Peel and quarter your onions and potatoes.
Preheat the oven to 375 degrees Fahrenheit.
Use a grater or food processor to shred onions and potatoes. Traditionally, these are grated, but either way works fine. The texture and size of the bits will differ based on which option you use. If you are using a food processor, you will likely have to shred the veggies in batches, because there is so much of them. Do not overload the food processor.
Place the potatoes and onions in a cheesecloth and wrap tight like a tourniquet. Squeeze the liquid from them and set that liquid aside. Do not discard it. The onions and potatoes should be moved to a clean bowl, and you will have to do this process a few times to squeeze out all the liquid from the entirety of the veggies. Your cheesecloth may tear occasionally, and if it does, you cannot use it as a tourniquet any longer. Just replace it with another piece and continue.
Pour the liquid off but keep the starch back. Allow the liquid to settle for a few minutes and then pour out the liquid, saving the potato starch and setting it aside.
Next, place the eggs and egg whites in a mixing bowl and beat. Use the whisk attachment on an electronic mixer or beat by hand with a whisk. Beat the eggs on a medium-high speed until their color becomes lighter and the volume is doubled. This should take about 3-4 minutes.
Add to the eggs the potato starch, salt, pepper, ¼ cup of the schmaltz, and baking powder. Combine all of that and then add in the potatoes and onions, mixing lightly.
Grease a baking dish (9x13 is ideal) and let it warm in the oven. You can grease it with two tablespoons of schmaltz or oil if you like. It should be preheated for about five minutes.
Pour your kugel mixture into the baking dish and level it out without pressing down. Bake for 40-50 minutes, or until golden brown. You can check the internal temperature of the kugel to see if it is cooked. It should read 160 degrees Fahrenheit.
The last step involves broiling the kugel, and you need to turn on your broiler to high for this. Broil for about 2-3 minutes, and the top should become a rich, brown color. Then, remove the kugel from the broiler and cut into slices, garnishing with your chives and parsley.
