In the bowl of a stand mixer, beat the butter on medium speed until creamy, about 1 minute. Scrape down the bowl. Add the brown and granulated sugars and beat on medium speed until light and fluffy, 2 to 3 minutes, stopping once to scrape the sides of the bowl.
Then add egg, molasses, sourdough discard, vanilla, fresh ginger. Mix on low speed until mostly combined.
Grab a bowl and add the flour, baking soda, cinnamon, and salt. Stir, then add to the bowl that’s on the stand mixer. Mix on medium speed until mostly combined, a few flour streaks are okay. Remove bowl and use spatula to clean the sides and bottom of the bowl to make sure everything is incorporated.
Cover and refrigerate dough for 45 minutes (up to overnight – the longer you refrigerate, the more flavor they will have). When the 45 minutes is up, keep the dough in the fridge and preheat oven to 400 degrees F.
When oven is preheated, line sheet pan with parchment paper and scoop dough into 55 gram balls; place 8 of them onto baking sheet. Press a little flaky salt into the top of each dough ball.
Turn oven down to 375 degrees F and bake cookies for 10 minutes, open oven and pick edge of baking sheet up and drop onto rack. Shut oven door and bake for another 3ish minutes until edges are just golden and center looks melty and slightly underbaked. Remove pan from oven and bang pan on the counter. Let cookies sit on the cookie sheet for 5 minutes, as they will continue to bake on the sheet. Then move cookies to a cooling rack.