How to Make It
In a medium bowl, combine the squash with the scallions, jalapeño, egg, flour and baking powder and season with salt and pepper. Mix gently just to combine.
In a large nonstick skillet, heat 2 tablespoons of the oil. Spoon 3 heaping 1/3-cup mounds of the batter into the skillet and press lightly to flatten them. Cook over moderate heat until golden, about 3 minutes. Flip the pancakes, add 1 tablespoon of the oil and cook until golden and crisp, 2 minutes longer. Drain on paper towels. Repeat with the remaining oil and batter. Serve the pancakes hot with lemon wedges and sour cream.