Preheat oven to 425 degrees and line a baking sheet with parchment paper or a slicone baking mat.
In food porcessor fitted with dough hook (or with pastry mixer or 2 forks) combine the flour, baking powder, baking soda, salt, and orange zest. Add the butter and process until butter is dispersed throughout dough and is the size of peas. Add in egg and buttermilk and combine, but do not overmix. Add in chocolate and turn onto floured surface and knead until dough just comes together. Pat down to ½ inch thickness and cut into 18 small triangles.
Bake for 12-15 minutes or until golden and puffed up.
For the glaze: Combine the powdered sugar and juice of an orange, adding more water if needed. Drizzle over warm scones and serve.