Line two large baking sheets with silicone mats or parchment paper.
Place butter in a saucepan over medium heat and let it melt and brown, (until it is a beautiful amber color.) Remove from heat and set aside for 10 minutes so it slightly cools.
In a mixing bowl, whisk together the flour, powdered milk, baking powder, baking soda and salt.
In your stand mixer bowl, add the browned butter, brown sugar, granulated sugar and vanilla extract. Beat together until well combined.
Add in your eggs one at a time and beat for about 2 minutes.
Add in the flour mixture and mix on low speed until combined.
Add in the chocolate chunks and pecans and mix on low speed until combined.
Scoop the cookies on to the baking sheets using a medium cookie scoop, leaving at least 2-1/2 inches between cookies
Freeze the cookie dough on the baking sheets for 20 minutes.
Preheat your oven to 350
Bake the cookies at 350 for 11-13 minutes.
Remove pan from oven and let cookies sit for 15 minutes on the pan, (you can press extra chocolate chunks in to the top to make them cute if you like and this is when you can sprinkle with optional flakey sea salt!)
Gently transfer to cooling rack and try not to eat all of them at once.