Preheat oven to 425 degrees F. Set the oven rack at the lowest level. Grease a 10-inch cast iron pan with butter.
Mix the dry ingredients. In a large bowl, mix together the flour, baking powder, and salt until combined.
Cut in the butter. Using a pastry cutter or back of a fork, cut in the 6 tablespoons of cold butter, until the mixture resembles coarse crumbs. Stir in the chives.
Add the wet ingredients. Add 1 cup buttermilk to the flour mixture. Stir to combine, and add more milk as necessary until the dough just comes together but is still moist. Be careful not to overwork the dough or the biscuits may come out dry.
Form the biscuits. Place the dough on a floured surface. Gently press the dough until 1 inch thick. With a 2-inch round cutter, cut the dough into 16 biscuits.
Bake the biscuits. Place the biscuits next to each other in the prepared pan. Bake on the bottom rack for 12-17 minutes or until golden brown. Brush with the 3 tablespoons melted butter. Cool slightly before serving.
SNAPPY TIPS: Be sure to keep your butter cubes and buttermilk as cold as possible before mixing them into the other ingredients. If you don't have a cast iron pan, you can also bake these biscuits on a buttered sheet pan.SNAPPY SUBSTITUTIONS: Instead of chives, you can use chopped cooked bacon, shredded cheese, or even chopped precooked onion.