Mix the dry ingredients. In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt.
Prep the butter. Slice the butter into 1-inch cubes by taking a stick of butter and using a sharp knife to halve it lengthwise. Flip the butter on its side and halve it lengthwise again. At this point, you should have four long columns of butter. Hold the columns together and slice crosswise into rough 1-inch pieces—there’s no need to be precise!
Cream the butter and sugar. In the bowl of a stand mixer fitted with the paddle attachment, combine the butter and sugar. Beat on low speed for 1 minute to soften the butter, then increase to medium-high and beat until light, fluffy, and doubled in volume, 2 to 3 minutes. Use a rubber spatula to scrape down the bottom and sides of the bowl as necessary.
Add the dry ingredients. With the mixer on low, gradually add the dry ingredients. Increase to medium-low and beat until the dough clumps around the paddle and/or the sides of the bowl, 2 to 3 minutes.
Form the dough. Tip the dough out onto the counter and use your hands to shape it into a rough disc. Use a bench scraper to divide the disc in half. Place one half on a piece of parchment paper around the size of a half sheet pan. Place a second sheet of parchment over the dough, creating a parchment “sandwich” with the dough in the middle.
Roll out the dough. Use a rolling pin to flatten the dough between the parchment sheets, working from left to right. Turn the dough 90 degrees and repeat every so often—doing so will help prevent the dough from cracking as you roll it. If the parchment starts to wrinkle and leave creases in the cookie dough, pull the sheet loose and smooth it before rolling the dough more. Continue rotating and rolling until you have a slab of cookie dough between ⅛ and ¼ inch thick. Don’t worry too much about the size and shape of the slab! It doesn’t really matter since you’ll be cutting out cookies from this slab. Chill the dough. Transfer the slab of cookie dough, still in between the parchment, to a half sheet pan. Freeze while you roll out the dough for the second disc.
Prep the oven. Once both your cookie slabs in the freezer, prep the oven. Position a rack in the center of the oven and preheat the oven to 325°F.
Prep the pan. Once the oven is preheated, remove the first sheet pan of dough from the freezer. Use the overhanging parchment as handles to carefully lift the slab of dough off the sheet pan and onto the counter. Peel the top layer of parchment from the slab and use it to line the sheet pan once more.
Cut out the cookies. Use a 1 ½ inch round cookie cutter to cut out circles, placing the cookies at least 1 inch apart on the prepared sheet pan. The dough should still be cool and firm to the touch. If not, freeze the sheet pan of cookies for at least 10 minutes before baking.
Bake the cookies. Bake one pan at a time (keeping the other pan in the refrigerator) for 15 to 18 minutes, or until small hairline cracks are visible on the surface of the cookies. Cool the cookies on the pan on a wire rack for 20 minutes, or until the edges and bottoms of the cookies are set and feel firm to the touch, then turn out to cool completely. Repeat to bake the remaining cookies.