Step 1

Preheat oven to 475°F. Stir together flour, cheese, chives, baking powder, pepper, salt, garlic powder, and baking soda in a large bowl. Whisk together buttermilk and mustard in a small bowl. Grate frozen butter into flour mixture using the large holes of a box grater; stir until well coated. Add buttermilk mixture; stir until just combined.

Step 2

Drop batter in 2 1⁄2- to 3-tablespoonful rounds onto 2 baking sheets lined with parchment paper, leaving 3 inches between rounds.

Step 3

Bake in preheated oven until biscuits are golden brown, 14 to 18 minutes, rotating baking sheets between top and bottom racks halfway through baking time. Brush biscuits with melted butter; garnish with sliced chives. Serve warm.