Cut the butter into small cubes and measure out the buttermilk. Place both back in the fridge to keep cold until they are needed.
In the bowl of a stand mixer fitted with a paddle attachment or a food processor, combine the dry ingredients.
Stir well to combine and break up any large pieces of brown sugar. Smaller lumps are ok.
Take the butter from the fridge and sprinkle it around the flour mixture int he bowl, trying not to handle it too much.
Blend on medium speed (or pulse in the food processor) until the butter is the size of peas.
With the mixer on, slowly stream in the buttermilk until the dough just comes together. There will still be a tablespoon or so of dry flour at the bottom of the bowl.
Turn the dough out onto a floured surface being careful to pour the dry flour onto the top of the dough so it can be folded in.
Knead the dough just a few times with your hands until it comes together and isn't very sticky. Be careful not to handle the dough too much as that will make the scones tough.
Divide the dough in half and pat each half into a circle about 8 inches in diameter.
Place each circle in a zip-top bag or wrap tightly in cling wrap and place them both in the refrigerator until the oven is preheated and you are ready to slice and bake them. They are best if left in the fridge overnight but are still delicious if baked the same day.
Preheat the oven to 400°. Once it is preheated, remove the scone circles from the refrigerator and place on an ungreased cookie sheet.
Slice each circle into 8 triangles.
Separate the triangles so they aren't touching and bake just until the edges begin to brown. This will take about 14-16 minutes. Do not overcook the scones or they will be dry.
Let the scones sit for just a few minutes once they are out of the oven and then serve them with soft butter, lemon curd, jam, and fresh whipped cream.