Prepare the Dry Ingredients: Preheat oven to 425°F. Line a baking sheet with parchment paper. In a large bowl, whisk together the flour, baking powder, garlic powder, salt, and cayenne pepper.
Incorporate the Butter: Add the cold, grated, or finely diced butter to the flour mixture. Use your fingers to quickly work the butter into the flour until the mixture resembles small pebbles.
Add Wet Ingredients and Cheese: Pour in the cold milk and stir in the shredded white cheddar cheese with a spatula until the ingredients are just combined. Be careful not to overmix.
Shape the Dough: Lightly flour your work surface and turn the dough out onto it. Gently gather and knead the dough just until it forms a cohesive mass.
Roll: Use a rolling pin to roll the dough to about 1/2-inch thickness.
Cut Using a sharp knife, cut the rectangle into 9 equal rectangular biscuits. Arrange the biscuits on the prepared baking sheet. Brush the tops of the biscuits with a little extra milk.
Bake: Bake the biscuits for 16–18 minutes, or until they are golden brown and cooked through.
Serve: Remove from the oven and serve immediately while warm.