Preheat waffle iron. In a mini prep food processor, puree the hulled strawberries. Beat egg whites until stiff peaks form. Mix milk, butter, egg yolks and sugar so that the sugar dissolves. Mix the flour, baking powder and salt in a large bowl. Add the wet ingredients to the dry ingredients. Mix until only some lumps remain in the batter. Do not overmix. Fold in the egg whites. Pour in preheated waffle iron and cook for 4 minutes.