Line two sheet pans with parchment paper. Mix dry ingredients in a medium sized bowl or food processor--flour, sugar, baking powder, baking soda, salt and chocolate chips. Cut in butter using your finger, pastry cutter or food processor. Mixture should look like coarse meal with visible various sizes of pieces of butter from peas sized to lima bean size. Mix buttermilk and coffee together. Pour over flour butter mixture. Using a rubber spatula, mix to just combine until no dry patches remain. Pour dough out onto a double strength sheet of plastic wrap. Pull the edges up and around dough to form a "kiss". Massage dough through the wrap until comes together into a dough ball. Divide the dough into two packages of plastic wrap and flatten to a round about 1 1/2-2" thickness. Chill for at least 2-3 hours or overnight. When ready to bake, preheat oven to 375º. Cut each round into 6 wedges and place on prepared sheet pans, leaving a couple of inches between. Brush with egg wash and sprinkle with sugar. Bake for 30-35 minutes, turning pans halfway through baking time, until golden brown on the bottoms and dry on top.
Notes
This scone dough freezes nicely. Score scones into wedges and freeze on a sheet pan or cardboard, tightly wrapped. Add about 5-7 minutes to baking time if cooking frozen.
