1. Chill the butter so it's very cold.
2. Slice the butter into small cubes, place in a bowl, and transfer the bowl to the freezer to chill. 
3. Preheat the oven to 425°F and line a baking sheet with parchment paper. Set aside.  
4. In the bowl of a food processor fitted with the 'S' blade, combine the brown rice flour, sweet white rice flour, tapioca flour, cornstarch, potato starch, xanthan gum, baking powder, baking soda, sugar, and salt. Pulse together until completely combined. Add the cold butter pieces to the flour mixture in the food processor and continue to process until the butter is completely cut into the flour and the mixture is consistent in texture. Transfer the mixture to a large mixing bowl and place in the freezer. 
5. Using the shredding disc of the food processor or a hand grater, shred the pear. Place the pear shreds in a mesh strainer over a bowl and press on the shreds so that they realize their moisture. Set aside. 
6. Remove the flour mixture from the freezer and add the buttermilk, gently mix until the dough begins to come together. Add 1/2 cup of the shredded pears and the dark chocolate chips to the bowl and fold to incorporate.   
7. Lay a large piece of plastic wrap over your kitchen counter and turn the dough out on top of it. Working quickly, use the edges of the plastic wrap to help you gather the dough into a mass and gently pat into a thickness of  ¾-inch. 
8. Cut the dough into 3-inch squares with a knife or into rounds with a floured biscuit cutter. 
9. Arrange the biscuits no more than 1-inch apart on a baking sheet, sprinkle with sparkling sugar, and bake in the oven for 15 minutes or until golden and cooked through. 
10. Once golden brown and cooked through remove the scones from the oven and allow to cool completely on a wire rack.  

To make the pear icing (optional): 

Combine the powdered sugar and pear juice in a bowl, beat with a whisk until completely combined. Drizzle over completely cooled pear scones and allow to sit at room temperature until the icing sets.