Preheat oven to 375 degrees and line two baking sheets with parchment paper.
In a medium size bowl, whisk together the flour, cocoa powder, baking soda, and salt. Set aside.
In a large bowl cream the butter and white sugar. Add in the light brown sugar, vanilla extra, sourdough discard, and egg. Beat well with a stand mixer or hand mixer until all ingredients all incorporated.
Slowly add the dry ingredients to the wet ingredients and mix until just combined.
Add one cup of chocolate chips to the batter and stir until incorporated.
Using a cookie scoop or a heaping tablespoon, scoop out equal portions of cookie dough and space about 1.5 inches to 2 inches apart. My cookie dough weighed about 34 grams per scoop.
Bake for 9-11 minutes or until the edges are firm. Remove from oven and let cool on the pan for 3-5 minutes, then transfer to a wire cooling rack.
Optional: For decorative purpose, remove cookies from the oven when they are almost done, top with chocolate chips, and finish baking.
Cookies can be stored in an airtight container on the counter for 5-7 days, or kept in the freezer for up to three months.