preheat oven to 400. grease shallow 1 1/2 quart casserole
in 4 quart saucepan, heat water, 1/2 tsp salt, and half of the milk to boiling on high. reduce heat to med-low and whisk in cornmeal in slow steady stream. cover and simmer 10 minutes or until mixture is very thick and pasty, whisking frequently.
remove from heat and whisk in margarine until melted. continue whisking and add remaining milk in slow steady stream. whisk in eggs 1 at a time, then add baking powder.
stir in green onions, corn, parmesan and 1/4 tsp pepper until mixed. transfer to prepareddish and spread in smooth even layer. (casserole can be cooled, then covered and refrigerated, up to 4 hrs before baking,
bake 45 minutes to 1 hour or until golden and knife inserted in center comes out clean. garnish with green onions.