Combine first 7 ingredients in a large bowl. Combine egg yolks, milk, and pumpkin; add to flour mixture, stirring just until moistened. Stir in melted butter. Set waffle batter aside. Beat egg shites at high speed with an electric mixer until soft peaks form, gently fold into batter. Bake in a preheated, oiled waffle iron until crisp. Serve with butter, maple syrup and toasted pecans.