Combine the plain flour, baking soda, salt , in a bowl and mix well. Keep aside. Combine the granulated sugar, Brown sugar and butter in a bowl and whisk well till no lumps remain. Add the vanilla essence, Peanut butter and Whisk well.
Add the dry ingredients , chopped pecan and mix well to form a dough. Divide the mixture into equal portions and shape each portion into a round ball and flatten the balls lightly.
Place the cookies on a greased baking tray and bake in a pre-heated at 180 c (360 f) for 10 to 15 minutes. Cool on a wire rack and store in air-tight containers.