Combine first 4 ingredients in a medium bowl; add milk and butter, whisking until blended. Stir in egg yolks until blended.
Beat egg whites at medium speed with an electric mixer until stiff peaks form. Fold egg whites, rice, and green onions into flour mixture.
Pour about 1/4 cup batter for each pancake onto a hot, lightly greased griddle. Cook pancakes 2 to 3 minutes or until tops are covered with bubbles and edges look cooked; turn and cook 2 to 3 minutes. Garnish, if desired.