Brown the Butter: Melt butter in small saucepan, stirring often. Watch for color to change from creamy yellow to golden tan or amber. As it foams, you will be looking for small brown bits to form. Remove from heat and pour into small bowl. Chill in refrigerator for 1 hour.
Preheat oven to 350°F and prepare parchment sheets or pan.
In a bowl, combine flour cornstarch, baking soda, and salt.
In a stand mixer bowl, cream together butter and sugars.
Add eggs and vanilla to creamed mixture and blend gently to combine.
Pour in dry ingredients and mix well.
Gently fold in chips, chunks, and nuts by hand. Do not use mixer.
Scoop 1 dozen at a time onto cookie sheet and bake for approximately 10 mins.
Remove from oven. Wait 5 minutes and carefully transfer cookies to cooling rack.
Repeat with rest of cookie batter.