01 -
Preheat the oven to 375°F (190°C). Grease a 2-quart baking dish.
02 -
Place squash into a large saucepan, cover with water, and bring to a boil. Boil until soft, 10 to 15 minutes.
03 -
Drain squash well, transfer to a large mixing bowl, and mash until slightly chunky.
04 -
Stir in 1/2 cup bread crumbs, onion, eggs, 1/4 cup melted butter, sugar, salt, and pepper until thoroughly combined.
05 -
Spread mixture into the prepared baking dish. Drizzle remaining 1/4 cup melted butter over top, then sprinkle with remaining 1/4 cup bread crumbs.
06 -
Bake in the preheated oven until cooked through and golden brown on top, about 1 hour.