Two key techniques make these whole-grain biscuits light and fluffy: smashing the butter into the flour mixture with your fingers, and folding the dough to create layers.
How to Make It
Preheat oven to 450°F. Whisk together flour, baking powder, salt, baking soda, and pepper in a large bowl.
Cut 7 tablespoons butter into 1/2-inch cubes; add to flour mixture, and combine with hands, smashing butter between your fingers until all cubes are mixed into the flour and flattened (you will have noticeable pieces of different sizes). Stir in thyme.
Add buttermilk; stir with a rubber spatula until flour is fully absorbed. Shape dough into a rough ball; turn out onto a lightly floured surface.
Gently pat dough into a 1/2-inch-thick square; fold dough in half, and pat into a 1/2-inch-thick square. Fold in half again. Repeat folding-and-patting procedure once more. Pat dough to a thickness of about 3/4 inch.
Cut dough using a 1 3/4-inch round cutter. Gather dough scraps, and pat to a 3/4-inch thickness 2 more times to yield 20 biscuits. Place biscuits 1 inch apart on a parchment paper–lined baking sheet.
Bake at 450°F until golden brown, 12 to 14 minutes. Place remaining 1 tablespoon butter in a small microwavable bowl; microwave at high until melted, 15 to 20 seconds. Brush tops of hot biscuits with melted butter, and serve immediately.