Sift together flour, salt and sugar. Take warm milk in a glass bowl and sprinkle yeast. Stir to dissolve. Beat egg yolks and add to yeast mixture along with vanilla essence.
Add flour mixture to liquid ingredients. Melt butter. When the melted butter has cooled slightly, add and stir to combine thoroughly. Beat egg whites until stiff and carefully fold into the batter.
Let mixture stand in a warm place about forty-five minutes or until mixture doubles in size. Heat the waffle grid and pour about half cup batter into the bottom half of each slot.
Close lid and cook until golden (or till almost all the steam stops flowing out of the grid) which will take about three to four minutes. Serve hot with maple syrup.