Step 1

Place a wire rack in a rimmed baking sheet; line with 2 layers of paper towels. Combine breadcrumbs, salt, baking powder, and pepper in a small bowl.

Step 2

Using the large holes of a box grater or a food processor, grate potatoes and onions. Transfer to a large kitchen towel. Gather ends of towel in each hand and twist over sink, wringing out as much liquid as possible. Open towel; toss mixture to loosen. Wring out again (excess moisture will lead to soggy latkes).

Step 3

Transfer potato mixture to a large bowl; add breadcrumb mixture and egg. Toss with your hands to thoroughly combine.

Step 4

Preheat oven to 425°. Heat 2 Tbsp. schmaltz and 2 Tbsp. oil in a large skillet over medium-high. Drop a small amount of latke mixture into skillet. If the fat sizzles around the edges, it’s ready (do not let it smoke). Working in 5 batches and adding more schmaltz and oil to skillet as needed to maintain about ⅛" fat, drop small spoonfuls of mixture into pan, pressing gently with the back of the spoon or a spatula to flatten slightly. Cook latkes, occasionally rotating pan, until golden brown and cooked through, about 2 minutes per side. (You may occasionally need to pick out stray potato bits from oil if they start to burn.)

Step 5

Transfer latkes to prepared rack and let drain. Remove paper towels and bake latkes in oven until all are warmed through and recrisped, about 5 minutes.