3 pounds russet (baking) potatoes
2 medium onions (about 12 ounces), peeled and cut into chunks
2/3 cup matzo meal
1 tablespoon salt
3/4 to 1 teaspoon freshly ground black pepper
3 tablespoons oil (for a pareve pudding) or melted Schmaltz
Preheat the oven to 350 F.
Peel the potatoes and cut into chunks to prepare them for the food processor. Reserve in a bowl of cold water until ready to process, but don’t leave them there longer than 2 hours.
In a very large bowl, beat together the eggs until well mixed. In the bowl of a food processor fitted with the metal blade, pulse the onions until very finely chopped, but not liquefied. Scrape the onions into the bowl with the eggs and stir them in. Stir in the matzo meal.
Drain the potatoes, then set a strainer over a bowl. In the same processor bowl (no need to clean), process the potatoes in three batches, until very finely chopped. The pieces should be no bigger than a grain of rice and mostly smaller.
As each batch of potatoes is processed, immediately scrape it into the strainer. With a rubber spatula or the back of a spoon, press out the moisture so it drains into the catch bowl.
Immediately stir the potatoes into the egg mixture. Discard the liquid and potato starch collected in the bowl. Season the batter with salt and pepper.
Pour 2 tablespoons of the oil into a 13- by 9-inch baking dish, preferably heatproof glass. Tip the pan so the oil coats the pan bottom and halfway up the sides. Warm the empty pan in the preheated oven for 5 minutes.
Protecting your hands, remove the hot pan from the oven and fill with the kugel mixture. The oil will rise up the sides of the pan, especially in the corners. It’s a good thing when the oil spills onto the surface of the batter, as it adds crispness to the finished dish. Press the batter down near the corners lightly to fill them with potato batter. Drizzle the surface with the remaining 1 tablespoon of oil.
Bake for 1 hour and 15 minutes, until lightly browned. Let rest for at least 15 minutes before cutting and serving, preferably somewhat longer. Serve hot or warm, freshly baked or reheated.
The kugel reheats extremely well in a 350 F oven, uncovered so the top can re-crisp. Reheating time depends on the size of the piece being reheated and the temperature of the kugel before it goes into the oven. It can be kept in the refrigerator, tightly covered, for at least 4 days, and for several months in the freezer. It is best to defrost in the refrigerator before reheating.