Preheat oven to 375 degrees Fahrenheit.

Butter the sides and bottom of a 4-cup souffle or casserole dish.

Warm the buttermilk in a saucepan over medium heat.

Stir in the cornmeal.

Cook, stirring often, until the mixture is thick and smooth, about 3 minutes.

Stir in the butter and salt.

Remove from heat and let cool slightly.

Whisk egg yolks and cheddar cheese into the cornmeal mixture.

Add the sliced green onions and stir well to combine.

In a separate bowl, beat the egg whites until soft peaks form.

Gently fold the beaten egg whites into the cornmeal mixture, a little at a time, to avoid deflating the whites.

Scrape the mixture into the prepared baking dish.

Bake for 25-30 minutes, or until puffed, golden brown, and set.

Serve immediately by spooning onto individual plates.