Position a rack in the center of your oven and preheat to 350°F / 175°C.
Pour the vegetable oil into a 9x9 inch or similar medium-sized casserole dish and place it in the oven to heat up while you prepare the batter.
Peel the potatoes and onion.
Using the coarse side of a box grater or a food processor with the grating attachment, grate the potatoes and onion.
Work quickly to prevent the potatoes from browning.
Transfer the grated potato and onion mixture to a large bowl.
Add the lightly beaten eggs, salt, and a generous amount of freshly ground black pepper.
Stir everything together until just combined.
Carefully remove the hot casserole dish from the oven.
Pour the potato mixture into the hot oil—it should sizzle!
Spread it into an even layer with a spatula.
Bake for 1 hour, or until the kugel is puffed, deeply golden brown, and crispy on top and around the edges.
Let the kugel rest for 5-10 minutes before slicing.
Serve hot, garnished with fresh chives and a dollop of sour cream or a side of applesauce.
Do not skip preheating the oil in the casserole dish.
Pouring the batter into sizzling hot oil is the secret to achieving that coveted crispy, non-stick crust.
Mix the batter until the are just combined. Overmixing can release too much starch and result in a gummy texture.
