Step 1

Shred potatoes with the grating disk of a food processor. After every 2 or 3 potatoes, wrap shreds in cheesecloth that has been folded over twice. Tie corners around the handle of a wooden spoon and twist bundle until water flows out. Collect water in a bowl and squeeze all potatoes until dry. Transfer potatoes to a large mixing bowl along with diced onion.

Step 2

Let drained potato water sit, undisturbed, until a pool of brown water forms on top of a slurry of pale potato starch. Carefully drain off water, then mix starch into potato and onion mixture with your hands. Mix in eggs, one at a time, alternating with 1/4-cup additions of matzo meal, until latke mix can be formed into patties that just stick together in your hands. Add salt incrementally.

Step 3

Heat 1/2 inch oil in a cast iron skillet over medium-high heat until a shred of potato immediately bubbles when added to pan. Form a small amount of latke mix into a disk and fry on both sides until golden brown to test for seasoning. Taste and add more salt as needed.

Step 4

Form latke mix into patties about 4 inches wide and 1 inch thick in the center. Slide into pan, cooking no more than 4 at a time. Fry until a golden-brown crust forms on bottom, then flip with a slotted spatula and fork until same color is achieved on other side. Flip as needed to get a firm, darker-than-golden crust on both sides.

Step 5

Transfer to a sheet pan lined with paper towels to cool for 2 minutes, then serve with applesauce and sour cream at the table.