Step 1Place flour, salt, baking powder and sugar in large mixing bowl and stir with a fork until well mixed.
Step 2In another bowl, beat eggs with a fork until they are all the same color and well blended. Add milk and stir to blend with eggs. Pour egg mixture into dry ingredients. Using a large spoon, stir briskly until mixture is well blended. Add shortening and butter and beat until all ingredients are very well blended. (If you are making this 1 to 2 hours before making waffles, cover with foil or plastic wrap and let sit at room temperature. Otherwise, cover and refrigerate until needed; this should be within a few hours).
Step 3Spray cool waffle iron with nonstick cooking spray or turn on iron and, when warm, grease both sides with oil (newer waffle irons have nonstick coatings and don't require greasing). Close lid and, when waffle iron is very hot, open lid and pour about 1/2 to 3/4 cup batter into it. Don't cover whole surface of waffle iron, as batter will spread during cooking. You will learn how much batter to use by doing first waffle. Close lid and cook. After 3 to 4 minutes, check to see whether waffle is done. When waffle iron has stopped emitting steam, lift top of waffle iron carefully--you don't want to tear waffle. Waffle should be golden brown. If still pale, close top and bake 1 to 2 minutes.
Step 4When first waffle is done, lift lid of waffle iron and gently pry out waffle with fork. Continue with remaining batter.