Place a 9x13 baking dish or pan in the oven and preheat it to 400 degrees, allowing the dish to heat up inside. This is crucial for achieving that crispy crust.
Peel the potatoes, then use a food processor or hand grater to grate them into large shreds. The larger shreds will contribute to a better texture.
Place the grated potato shreds in a large mixing bowl and cover them with cold water. Let them sit for a few minutes to wash away excess starch.
Meanwhile, peel and shred the onions using the food processor or hand grater. Reserve the shredded onions for later.
In a medium mixing bowl, whisk together the eggs, salt, and black pepper until fluffy. This mixture will add moisture and flavor.
Drain the potato shreds in a colander, pressing down firmly to remove excess liquid. This step is important to avoid a soggy kugel.
Return the drained potatoes to a large bowl. Add the seasoned egg mixture, reserved onions, and potato starch. Use your hands to mix everything together until well combined.
Carefully take the preheated baking dish out of the oven. Quickly pour in 3 tablespoons of schmaltz or olive oil. Use a pastry brush to spread the fat around the bottom and sides of the hot dish. Be cautious to avoid burns!
Spread the potato mixture evenly into the baking dish (it should sizzle!), then drizzle the remaining 1 tablespoon of melted schmaltz or olive oil on top.
Bake uncovered at 400 degrees for 60 to 70 minutes until the top is nicely browned all over. If it starts browning too quickly, cover it to prevent over-browning. For a final touch, if it isn’t brown enough, place it 6 inches below the broiler for a minute or two to enhance the color.
Once baked, let the kugel sit for 5 to 10 minutes before slicing and serving. This waiting period allows it to set, making it easier to cut.