
Pre heat the oven to 350°F.
Slice yellow squash into 1/4 inch thick slices and boil until tender. Boil the squash for about 10 minutes.
Drain very well. This is important so the casserole does not become watery.
In a large bowl, stir together: cooked squash, onion, eggs, 2 tbsp melted butter, sugar, salt, and pepper.
Mix until everything is combined. Spread the mixture into a small baking dish.
Mix the bread crumbs with the remaining 2 tablespoons of melted butter. Sprinkle over top the casserole.
Bake at 350°F for 45 minutes, until hot and bubbly and the top is golden brown.
Let sit for about 5 minutes before serving.