Preheat oven to 375 degrees F/ 190 C. Line a baking sheet with parchment paper and set aside (you will need 3 baking sheets with parchment paper).
In a medium bowl mix the dry ingredients - flour, baking soda, baking powder and salt.
In a stand alone mixer cream together the softened butter and sugars until combined. You can also do this by hand but it is much easier in a mixer.
Add the egg and vanilla extract and beat until combined, about 1 minute.
Add the dry ingredients to the wet ingredients and mix until combined.
Remove the bowl from the mixer and fold in your chocolate chips or chopped up chocolate.
Fold in the chopped pecans.
Roll 2 tablespoon of cookie dough into balls and space them out on the baking sheet. You should have 6-8 cookies per sheet.
Bake them for 10 minutes. Take them out when they are just barely starting to turn brown. Rotate the sheets for even baking—cool the first batch on a cookie sheet while the second bakes.
Let them sit on the baking sheet for 5 minutes before moving them or eating them.
Notes
this makes 18 larger cookies or 36 small cookies
for chewier cookies you can use a mix of brown and white sugar
you can chill the cookie dough before baking for about an hour or more if you want cookies that will flatten more