How to Make It
Combine grated potatoes and water in a medium bowl; let stand 15 minutes.
Carefully drain liquid from potatoes, leaving potato starch in bottom of bowl. Add onion, flour, tempura flour, and salt; stir to combine.
Heat oil in a large nonstick skillet over medium-high. Add batter to hot oil in 4 separate portions; top evenly with jalapeño. Cook until edges begin to brown and small bubbles form on top of pancakes.
Turn pancakes, and press each down with a spatula to create thin pancakes. Cook until slightly crisp and cooked through, about 2 minutes. Serve immediately with Korean Pancake Dipping Sauce.