Melt butter in a large skillet over medium heat. Add in chopped pecans and cook, stirring occasionally, for 4 to 5 minutes, or until lightly toasted. Set aside until needed.
In a large bowl combine flour, cornstarch, salt, cinnamon, and baking soda; whisk well to combine then set aside until needed.
In a small saucepan, over medium heat, melt the remaining butter. Continue to cook the butter, swirling the pan occasionally. Keep a close eye here. The top of the butter should become foamy. And you should hear tiny popping noises. The butter will develop into a rich amber color, with tiny brown bits at the bottom. And it will have a slightly nutty aroma. Once the butter reaches this stage, remove from heat immediately and pour into a large mixing bowl.
Add both dark brown sugar into the mixing bowl and whisk well to combine.
Add in vanilla. Beat in eggs and egg yolk, one at a time, beating until eggs are just combined.
Using a rubber spatula, fold in the flour, stirring until just combined. Fold in the buttered pecans.
Cover bowl and refrigerate for 4 hours.
Preheat the oven to 375 degrees (F). Line two large baking sheets with parchment paper.
Using a large cookie scoop, divide the dough into 3-tablespoon sized balls and place onto prepared baking sheets, leaving about 3 inches between each ball of dough for spreading.
Firmly press a pecan half on top of each ball of cookie dough.
Bake, one tray at a time, in a preheated oven for 10 to 11 minutes. If any edges spread out while baking, use a spatula and gently press them back in as soon as you remove the cookies from the oven.
Sprinkle warm cookies with granulated sugar.
Allow cookies to cool on the pan for 15 minutes, then carefully transfer to a cooling rack.
