Preheat the oven to 400ºF. Line an 8x8-inch baking dish with floured parchment paper.
Mix the dry ingredients: In a large bowl, whisk together the flour, sugar, baking soda, baking powder, and salt.
Cut in the butter: Grate or cube the cold butter. Use a pastry cutter or your fingers to work it into the flour until the mixture resembles coarse crumbs with pea-sized bits throughout.
Add the buttermilk: Pour in the buttermilk and stir just until the dough comes together. It'll be shaggy with dry patches.
Fold: Transfer the dough onto the floured parchment. Pat it out into a rectangle, then fold it in thirds and press it down again. Repeat twice. TIP: Be very gentle with this movement, you are not kneading.
Roll and fill: Roll dough out into a rectangle about 15 x 12 inches. Brush evenly with cooled melted butter, then sprinkle with brown sugar and cinnamon.
Roll up and slice: Starting from the long edge, roll the dough up tightly. Slice into 8 pieces using a sharp knife or dental floss.
Arrange and bake: Place the rolls snugly into the prepared pan. Bake for 22–26 minutes. They should be golden and fully baked in the center (190ºF on a cooking thermometer)
Cool slightly before serving. If using glaze, wait about 10 minutes before drizzling over warm rolls.
Video
Notes
Use cold butter and buttermilk for the flakiest layers. Keep the dough cold until it goes into the oven.
Mix gently to avoid tough rolls. Biscuit dough needs minimal handling.
The dough is sticky. Use the parchment to help roll it up or slide a floured spatula underneath if needed.