Place flour, brown sugar, cinnamon, ginger, cloves, salt, and baking soda in a food processor fitted with the steel blade. Process until combined, about 10 seconds. Scatter the 12 butter pieces over the flour mixture and process until the mixture is sandy and resembles very fine meal, about 15 seconds. With the machine running, gradually add the molasses and milk and process until the dough is evenly moistened and forms a soft mass, about 10 seconds.

Alternatively, make the dough in a standing mixer fitted with the paddle: mix the flour, sugar, and spices on low until combined, about 30 seconds. Stop the mixer, add the butter pieces, and mix at medium-low until the mixture is sandy and resembles fine meal, about 1½ minutes. Reduce speed to low and, with the mixer running, gradually add the molasses and milk; mix until the dough is evenly moistened, about 20 seconds. Increase speed to medium and mix until thoroughly combined, about 10 seconds.

Scrape the dough onto a work surface and divide it in half. Work with one portion at a time. Place one portion between two large sheets of parchment paper and roll to an even 1/4-inch thickness. Repeat with the second portion if desired, stacking the rolled dough sandwiches.

Leaving the dough sandwiched between the parchment sheets, transfer the sandwich(es) to a baking sheet and freeze until firm, 15 to 20 minutes. (Alternatively, refrigerate the rolled dough 2 hours or overnight.)

When ready to bake, preheat the oven to 350°F (175°C). Line two cookie sheets with parchment paper.

Remove one chilled or frozen dough sandwich to your work surface. Peel off one parchment sheet and set it aside. Peel off the second parchment sheet so the dough is exposed (or leave the dough on the remaining parchment sheet for easier transfer if you prefer). Cut the dough into gingerbread people or round cookies.

Transfer the cut cookies to the prepared cookie sheets using a wide metal spatula, spacing cookies about 3/4 inch apart. Repeat cutting and transferring until the cookie sheets are full.

Bake the cookies one sheet at a time (or two if your oven allows even baking) at 350°F for 8 to 11 minutes, rotating the cookie sheet front to back halfway through baking. Bake until the centers are set and the dough barely retains an imprint when touched very gently with a fingertip. Do not overbake.

Cool the cookies on the baking sheets for 2 minutes, then use a wide metal spatula to transfer them to a wire rack to cool completely to room temperature.

Gather the scraps, re-roll between parchment to 1/4-inch thickness, cut, and bake as in steps 6–9 until all dough is used.

Once the cookies are completely cool, decorate with royal icing if desired. Store the cooled cookies in an airtight container at room temperature for up to 1 week.