In a medium bowl combine flour, baking soda, baking powder, and salt. Whisk to combine.
In a large bowl or the bowl of a stand mixer, combine butter, granulated sugar, and brown sugar. Beat together on high speed for 2-3 minutes or until smooth and fluffy, scraping down the sides of bowl as needed.
Scrape down the sides of bowl. Add vanilla and egg and mix on low speed until incorporated.
Add sourdough discard and mix until incorporated.
Gradually add dry ingredients and mix just until incorporated. Add chocolate chips and stir in by hand.
Cover dough and chill for at least 30 minutes, or overnight.
When ready to bake, preheat oven to 350°F. Line 1 or 2 large sheets pans with parchment paper. Scoop rounded tablespoons of dough and place on sheet pan, spacing 2 inches apart.
Bake for 10-12 minutes or until starting to lightly brown around the edges and just set in the center (they may look quite pale on top but they will continue to darken as they rest). Allow to cool for 1-2 minutes on the pan then slide parchment onto a wire rack to cool completely—don’t try to remove from the parchment until they are fully set.