Preheat your oven to 375°F (190°C) and grease a 1.5-quart casserole dish, 9-inch baking dish or 6 individual ramekins/cocottes.
In a large bowl, whisk together the white cornmeal, baking powder, sugar and salt.
Sperate the egg whites and yolks into separate bowls.
Bring the milk to a boil and stir into the cornmeal mixture until smooth.
With an electric mixer, beat the egg whites until stiff peaks form.
After allowing the cornmeal mixture to cool for about 10 minutes, stir in the egg yolks and melted butter.
Using a rubber spatula, gently fold the stiff egg whites into the cornmeal mixture. Do this in two batches, cutting down the center and sweeping the mixture up and over. The goal is to incorporate the whites without deflating the air. Stop folding when there are no visible streaks of egg white left.
Pour the light and airy batter into your prepared dish or mini serving dishes.
Bake the spoon bread for 35-45 minutes, until set. You should be able to poke the center of the bread and have a knife or toothpick some out clean. Some "jiggle" is still normal.
Serve warm with butter, or any other desired toppings.