How to Make It
In a small saucepan, whisk the molasses with the bourbon and cinnamon. Bring just to a boil, then cook over low heat for 2 minutes. Let cool completely.
In a food processor, combine the cooled molasses mixture with the butter and puree until smooth. Scrape the butter into a bowl and season with salt. Cover and refrigerate for 1 hour.
Preheat the oven to 450° and line a baking sheet with parchment. In a large bowl, whisk the flour with the baking powder, salt, 1 1/2 teaspoons of pepper and baking soda. Scatter the cubed butter over the dry ingredients and, using your fingers, pinch the butter into the flour to form small sheets of butter, with some of the butter about the size of peas. Stir in the 2 cups of buttermilk just until a dry, shaggy dough forms.
Turn the dough out onto a work surface and knead gently, folding the dough over itself 2 or 3 times to form a layered dough. Pat the dough out to a 1-inch-thick rectangle. Using a large, sharp knife, cut out as many 3-inch-square biscuits as you can. Gently press the scraps together and cut out more biscuits.
Arrange the biscuits on the prepared baking sheet. Brush them with buttermilk and sprinkle with coarsely ground black pepper. Bake for about 15 minutes, until golden brown. Serve warm with the bourbon-molasses butter.