With an electric mixer, beat the first 3 ingredients until smooth and creamy and set aside.
Preheat the oven to 350°F Combine the flour and sugar in a bowl. Using a pastry cutter, cut the butter into the flour and sugar until the mixture resembles coarse crumbs. Add the pecans, and use your fingers to toss together and incorporate into the mixture.
Spray a baking sheet with non-stick spray. Spread the crumble on the baking sheet and bake for 15 minutes until golden brown and crisp.
In a large bowl, combine all the dry ingredients. In a separate bowl, whisk together the egg, buttermilk, melted butter and vanilla. Pour into the dry ingredients and stir just until combined (batter should be lumpy). Stir in the pecans.
Let the pancake batter rest for 20 minutes before cooking the pancakes on a griddle or in a large pan. Top each pancake with some of the pecan crumble and maple syrup.