Melt the butter and set aside to cool.
Adjust your oven rack to the lower middle position and preheat the oven to 325 degrees. Line 2 baking sheets with parchment paper. Set aside.
Place pecans on a small baking sheet and bake for about 5-8 minutes or until lightly toasted. Remove from the oven to cool while preparing the cookie dough.
In a medium mixing bowl combine the flour, baking soda and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, beat the melted butter, brown sugar and granulated sugar on medium until smooth and lightened. Add the egg, egg yolk and vanilla. Blend on medium speed until combined. Reduce the speed to low and add the flour mixture in 2 additions, blending just until the flour disappears. Scrape down the sides and bottom of the mixing bowl with a rubber spatula, and mix again and well combined. Add the nuts and chocolate chunks and stir with a wooden spoon until combined.
Using an ice cream scoop that holds about 2 tablespoons, roll the dough into balls and place them 2-inches apart on the prepared cookie sheet. Bake the first sheet while rolling the remaining cookie dough. Bake for 17-20 minutes or until the edges are set and beginning to brown and the center are still soft and puffy. Rotate the sheet halfway through baking to ensure even browning.
Remove from the oven and let the cookies cool for 10 minutes before transferring to a wire rack. Or, if you are using a rimless baking sheet, slide the entire sheet of parchment and cookies onto the wire rack to cool.
Store in an airtight container at room temperature. If storing for more than one day, add a slice of sandwich bread to help the cookies stay soft and chewy.