Step 1
Preheat oven to 500 degrees F (260 degrees C).
Step 2
Mix flour baking powder and salt together in the bowl of a stand mixer with a paddle attachment. Add unsalted butter and mix at medium speed until well incorporated and the mixture resembles wet sand about 4 minutes.
Step 3
Remove the bowl from the mixer and fold in buttermilk until dough sticks together.
Step 4
Dump dough onto a flour work surface; pat into a rectangle. Pat remaining dry crumbs into the mixture by hand.
Step 5
Cut dough in half with a floured bench knife; stack cut halves on top of each other. Press layers together to about 1 1/2-inch thickness shaping a long rectangle as you go. Repeat 3 to 5 times.
Step 6
Cut dough into 8 even squares with the bench knife. Cut off uneven edges and put these scraps to the side; clean cuts on all sides will encourage rise. Pat scraps together to make 1 odd-shaped ninth biscuit.
Step 7
Place biscuits close together in a 9-inch square pan and brush with melted salted butter. Place pan on top of the warm stove for 10 to 15 minutes to rise.
Step 8
Bake biscuits in the preheated oven checking halfway through bake time until tops are golden brown and a toothpick inserted into the center comes out clean 14 to 18 minutes.