Preheat the oven to 350 degrees F. Spread the pecans on a baking sheet; bake until toasted, 5 - 7 minutes. Let cool, then chop. Reduce the oven temperature to 200 degrees F.
Whisk the flour, sugar, salt, baking powder & baking soda in a large bowl. Whisk the egg, milk, buttermilk & vanilla in a separate bowl until combined. Stir the egg mixture, melted butter & shortening into the dry ingredients until just combined. (The batter will be lumpy.)
Preheat a waffle iron & brush with melted butter. Ladle some batter into the iron (about 1/2 C, depending on your waffle iron); sprinkle with 2 Tbsp toasted pecans. Cook until golden brown, then transfer the waffle to a baking sheet & keep warm in the oven. Repeat with the remaining batter. Top the waffles with butter & maple syrup.