1. Place half the potatoes in the bowl of a food processor and process until finely chopped. Transfer potatoes to a strainer set over a medium bowl; let drain. Repeat process with remaining potatoes. Measure out 3 cups chopped potatoes and discard any remaining potatoes.

2. In a large bowl, beat eggs lightly. Add potatoes, onion, 1 teaspoon salt, and pepper; mix well. Stir in 2 tablespoons matzo meal, and let stand about 30 seconds to absorb moisture in batter. If necessary, add more matzo to make a thick, wet batter.

3. Place a large nonstick skillet over medium heat; add oil. When oil is hot, working in batches, add 2 tablespoons batter, flattening gently to make thick pancakes. Cook until browned, 2 to 3 minutes per side. Transfer to a paper towel-lined plate; season with salt. Repeat process until all the batter has been used. Serve immediately with applesauce and sour cream.