Cut the butter into cubes. Place the butter in the fridge to keep chilled until ready to use.
In a large bowl, whisk together the flour, salt, and baking powder.
Add the cold butter cubes to the flour. Use a pastry cutter (or two knives) to crumble the butter into the flour mixture, until the butter resembles coarse crumbs.
Pour the milk into the the flour mixture, stirring just until combined. Using a wooden spoon and then your hands (gently kneading the dough if necessary), form the dough into a ball.
Sprinkle a parchment-covered surface with a small amount of extra flour. Form the dough, using your hands, into a long rectangle. Fold the dough in half, lengthwise and gently press together.
Using a biscuit cutter, cut out individual biscuits. Place the biscuits on a sheet pan or stone. I like to line my sheet pan with parchment paper. Brush the top of each biscuit with the 1 tablespoon of milk, if desired. Another option is to use melted butter instead of the milk.
Bake for 17-20 minutes, until the tops are golden and the sides are firm. The time it takes for your biscuits to bake will depend on the size of the biscuits, so keep an eye on them through the oven door. I make fairly large biscuits.
Notes
If you're making a sweet biscuit, you could add 1-2 tablespoons of cane sugar to the dry ingredients. To Freeze:Place the uncooked, cut-out biscuit dough on a cookie sheet. Freeze the raw biscuits until frozen (about 30 minutes-1 hour). Once frozen, place the biscuits in a freezer-safe bag or container. When you’re ready to cook a biscuit, follow the cooking directions in the recipe above. You'll need to add additional time for cooking the biscuits, so keep an eye on the biscuits while they bake. Another option is to bake the biscuits, allow to cool, and then freeze the biscuits fully cooked.