Sift the dry ingredients into the bowl of a food processor and pulse to combine. Then drop in the butter and pulse about 20 times until the butter is incorporated and the mixture has a coarse crumb texture.
Crack the egg into a glass cup measure and beat it. Add in the buttermilk until you have 3/4 cup liquid. Add in the vanilla and mix.
While pulsing the food processor, pour in the liquid, and stop the machine just as the dough comes together.
Turn the dough out onto a surface that has been lightly dusted with cocoa powder. Bring the dough together and gently roll out to about 1/2 inch thickness and cut into scones with a biscuit cutter. Reform the dough as necessary.
Put the scones on a parchment or silpat lined baking sheet and then into the refrigerator to chill while you clean up, at least 30 minutes, to overnight.
Just before baking, lightly sprinkle each scone with sea salt or other coarse salt.
Bake for about 15 minutes until risen and firm. Don't over bake.