In a medium bowl, whisk together the flour, baking soda, and salt. Set aside.

In the bowl of a stand mixer fitted with a paddle, beat the butter on medium speed until creamy, about 1 minute. Add the granulated and brown sugars and beat on medium speed until light and fluffy, 2 to 3 minutes. Scrape down the sides and bottom of the bowl, add the egg yolks and mix until fully incorporated. Add the sourdough starter and vanilla and mix on medium-low until fully incorporated. Scrape the sides and bottom again to make sure everything is incorporated.

Turn the mixer to low speed and add the flour mixture in two additions, scraping down the sides of the bowl and mixing until no flour streaks remain. Add the chocolate chips and mix until just combined. *Add the raspberries and mix very briefly until just combined. You want to incorporate them without mashing them into the dough. You may even remove the bowl from the mixer and gently fold in the raspberries by hand.

∗ Tip: The raspberries can thaw quickly, causing the dough to become messy and difficult to scoop. Optional step to avoid this- Once the chocolate chips are added, remove the bowl from the mixer and divide the dough into two equal portions. Fold half of the frozen raspberries into one potion of the dough (leaving the other half of the raspberries in the freezer). Scoop and freeze the cookies as directed below. Then, repeat with the other portion of the cookie dough.

Form the dough into balls weighing 70g, or about 4 tablespoons, each. Place the dough balls on a sheet pan, wrap tightly, and place in the freezer for at least 2 hours.

When ready to bake, place two racks in the upper and lower thirds of the oven and preheat to 375°. Line two half-sheet pans with silicone mats or parchment paper.

Remove 12 cookies from the freezer and place 6 frozen cookies per sheet pan. (The cookies will be baked from frozen.) Place the cookies in the oven and bake for about 18 minutes, rotating the trays halfway through the baking time. When done, the tops should be just set and the edges beginning to brown. Let cookies cool on the tray for 5 minutes and then transfer to a cooling rack. Repeat with the remaining cookies, or leave them in the freezer for future baking.