Step 1

Preheat oven to 450 degrees. In a large bowl, whisk together flour, sugar, salt, baking powder, and baking soda for 30 seconds. Toss butter into dry mixture to evenly coat, then press between your fingers to create flower-petal shapes and return to bowl.

Step 2

Slowly drizzle buttermilk over flour-butter mixture (to evenly distribute) while stirring with a fork. Stop stirring when dough begins to form but mixture is still crumbly. Transfer to center of a parchment-lined baking sheet. Gather dough with your hands, pressing firmly to bind, and flatten it into a 6-by-10-inch rectangle. Lift parchment along a short end of dough and fold in half, forming a 6-by-5-inch rectangle. Turn dough 90 degrees; gently reflatten to 6 by 10 inches. Fold in half again and flatten slightly into a 6-inch square.

Step 3

To keep things easy, form the dough on the same tray it's baked on. Cut it into thirds in both directions with a large, sharp knife, to form 9 biscuits. Brush tops with buttermilk. Bake until puffed, golden brown on top, and hollow-sounding when tapped on bottom, 16 to 18 minutes. Transfer to a kitchen towel-lined basket; cover to keep warm. Serve with butter and jam.