In the bowl of a stand mixer fitted with the paddle attachment, combine butter and sugars until fluffy.
Add the egg and vanilla and beat just until combined.
Add the flour, baking powder, and baking soda and beat again until just combined.
Using a rubber scrapper or wooden spoon, fold in pecans and chocolate chips.
The dough can be baked immediately or covered and chilled in the refrigerator for up to 72 hours.
When ready to bake, preheat the oven to 350ºF. Line a baking sheet with parchment paper or a Silpat. Scoop balls of dough onto the baking sheet and sprinkle with flaked sea salt if desired.
Bake cookies 13-16 minutes (it will take a little longer if the dough has been chilled) or until just beginning to brown around the edges.
Remove from the oven and allow to cool on the pan for 5 minutes before removing to a cooling rack to cool completely.