In a large bowl, place the gf pastry flour, baking powder, and salt, and whisk to combine. Add the shredded and chilled butter, and toss to coat the butter in the dry ingredients, breaking up any large clumps.
Add the shredded cheese, and toss to coat the shreds in the dry ingredients. Create a well in the center of the dry ingredients.
Add the cold buttermilk, and mix lightly to combine. The mixture should come together and everything should be just moistened in clumps.
If there are very crumbly bits, still, after mixing, add cold water by the teaspoon right on the dry parts. Mix again, and repeat as necessary.
Transfer the crumbly dough to a lightly floured piece of parchment paper. With clean, dry hands, lightly pat the dough into a rough square.
Sprinkle the round lightly with a bit of gf pastry flour, and roll it out into a square about 8-inches in diameter and about 1/2-inch thick.
Square the perimeter a bit by pressing the edge of a bench scraper or sharp knife up against the sides.
Fold the dough over on itself like a business letter and reroll as necessary for it to hold together and appear smooth on top.
Place the square dough into the freezer and chill until firm, about 10 minutes.
Preheat your oven to 375°F. Line a rimmed baking sheet with unbleached parchment paper and set it aside.
Remove the dough from the freezer and, with a floured bench scraper or large, sharp knife, slice perpendicular lines through the center of the dough, creating 4 equal rectangles.
In the same manner, slice each rectangle into 2 triangles. Place the triangles about 1 inch apart on the prepared baking sheet.
Brush the tops of each rectangle with a bit of optional cream, and sprinkle lightly with coarse salt.
Place the baking sheet in the center of the preheated oven. Bake until the scones are puffed and firm to the touch, and brown on the edges (18 to 20 minutes).
Remove the baking sheet from the oven. Allow the scones to set briefly before serving warm or at room temperature.