In a small bowl, whisk the flour, ginger, cinnamon, baking soda, salt, nutmeg, and pepper.
In a large bowl, beat the butter and brown sugar with a stand mixer fitted with the paddle attachment on medium speed until light and fluffy, about 3 min.
Add the egg yolk and molasses and blend until well combined, about 1 minute.
Add the flour-spice mixture and mix on medium-low speed until the dough is well blended and forms a pea-sized texture, 30 to 60 seconds.
Pour the dough onto an unfloured work surface; gently knead until it comes together.
Shape into an 8-inch-long log about 1-1/2 inches in diameter and wrap in plastic.
Refrigerate for at least 3 hours or overnight.
Preheat the oven to 350°F. Line a large cookie sheet with parchment.
Unwrap the dough and use a thin, sharp knife to cut the log into 1/8-inch slices. Arrange the slices about 1 inch apart on the sheets.
Bake until the cookies are slightly darker brown on the bottoms and around the edges, 10 to 12 min.
Set the sheet on a rack to cool for 15 minutes. Transfer the cookies to a rack and let cool completely. When cool, store in airtight containers.
Ginger flavor intensifies with time. When stored in an airtight container, the cookies remain impressively delicious.