Preheat oven to 450°F and line a baking sheet with parchment paper.
Sift flour, sugar, baking soda, and baking powder into a medium mixing bowl, add kosher salt and mix with a whisk to combine.
Add the cold cubed butter to the flour mixture and work it into the flour with the tip of your fingers until about pea size and larger. You want the butter pieces to be different sizes and more flat than round.
Make a well in the middle of the flour mixture and pour in the cold buttermilk. Fold with a spatula or wooden spoon until a shaggy dough forms.
Turn the dough out onto a well-floured board, pat the dough out to about 1/2” thick and fold it over itself. Do this two to three times and then shape the dough into a rectangle.
With a rolling pin, roll the dough out into a rectangle about 6”x14”. Fold in three like a letter. Roll the folded rectangle out one more time, and fold it again. This will create distinct layers when baked. Then if needed pat it down to about 1” thick. Cut into 6 squares.
Alternately, if you want to cut your biscuit into rounds, use a biscuits cutter, flour it well and push it straight down to cut without twisting. Cut as many as you can, and reshape the leftover per the above instructions and cut again until all gone.
Place the biscuits on the prepared baking sheet, close together, brush the top and sides with some extra buttermilk, sprinkle the top with sugar for sweeter biscuits or with some sea salt for more savory biscuits. Bake for 15 - 17 minutes until golden brown.