In a large mixing bowl, beat the softened butter and dark brown sugar on medium speed for 2–3 minutes. The mixture should look smooth and creamy rather than overly fluffy. Scrape down the sides of the bowl as needed.

Add the molasses, egg, and vanilla extract: Beat on medium-low speed until fully combined. The mixture should be thick, glossy, and evenly dark brown.

In a separate medium bowl, whisk together the flour, baking soda, kosher salt, ginger, cinnamon, cloves, and nutmeg. Mix thoroughly so the spices and baking soda are evenly distributed.

Add the dry ingredients to the molasses mixture in two additions. Mix on low speed just until the dough comes together and no dry flour remains. The dough should be soft and slightly tacky but firm enough to hold together. Avoid overmixing, which can make the cookies tough.

Divide the dough into two equal portions and flatten each into a disk about 1 inch thick. Wrap tightly and refrigerate for 45 minutes. The dough should feel firm enough to roll without sticking excessively.

Preheat the oven to 350°F (175°C). Line two large baking sheets with parchment paper. Lightly flour a clean work surface and rolling pin.

Work with one chilled dough disk at a time. Roll the dough to about ¼ inch thick. Use only enough flour to prevent sticking. Too much extra flour can make the cookies dry. If the dough cracks, let it sit at room temperature for 2–3 minutes before continuing.

Cut the dough using a 3- to 4-inch gingerbread man cutter. Transfer the shapes to the prepared baking sheets, leaving about 1½ inches between them. Gather the scraps and reroll gently. If the cutouts become very soft, refrigerate the baking sheet for 10 minutes before baking.

Bake for 8–10 minutes. The edges should look set, while the centers should still appear soft and slightly puffed. For the chewiest texture, avoid baking until the centers look dry. Bake additional trays as needed.

Let the cookies rest on the baking sheet for 5 minutes. Transfer them carefully to a wire rack and cool for another 20 minutes. They will firm up as they cool but should remain soft in the centers.

In a small bowl, whisk together the powdered sugar, milk, and vanilla extract. The icing should be thick enough to hold a piped line without spreading immediately. If needed, add a few drops of milk to thin it or a little more powdered sugar to thicken it.

Transfer the icing to a piping bag fitted with a small round tip. Pipe faces, buttons, cuffs, outlines, or other decorations onto the completely cooled cookies. Add optional sprinkles or mini chocolate chips while the icing is still wet.

Arrange the decorated cookies in a single layer: Let the icing dry for about 30 minutes, or until firm enough to touch lightly without smearing. Once set, the cookies can be served or stored.