In the bowl of a food processor fitted with the blade, combine the flour, baking powder, baking soda, and sugar and pulse to combine. Lay the butter on top of the flour and pulse several times until butter is the size of large peas and the mixture looks crumbly. With the machine running, pour in the buttermilk and process just until mixture begins to form a ball and the processor wants to stop.

 Lightly dust a work surface, put the raisins on top, then top with the dough. Knead lightly to bring the dough together and incorporate the raisins. Only if necessary, add a little more flour to the surface to prevent dough from sticking. Pat or roll the dough into a ¾” – 1” thick disk. Use a 3” cutter to cut rounds out of dough as close together as possible. Gather the scraps and knead them together 2 or 3 times, then flatten the dough and cut out more biscuit rounds. (Alternately, shape the dough into a large rectangle and cut into 3” squares, making sure all edges of each biscuit have a sharp cut edge.)

 Transfer the biscuits to a large baking sheet lined with parchment paper and refrigerate 30 minutes. Preheat the oven to 375° while biscuits are chilling. Brush tops with egg wash and bake  for 12-15 minutes or until golden. Transfer to a wire rack to cool completely, then glaze if desired.

 Glaze: Combine sifted powdered sugar with a small amount of half and half and whisk to form a thick, smooth glaze. Spread glaze over cooled biscuits and let stand until dry.

* If fruit is very dry, put it in a small saucepan with ¼ c. water over low heat and bring water to a simmer. Cover, remove from heat, and let stand for 15 minutes, stirring occasionally to help all the fruit plump evenly. Transfer to a paper towel and spread out to remove any excess moisture before adding to the dough.

 Baked tea biscuits can be wrapped individually and frozen for several months. Unwap glazed biscuits before thawing to prevent glaze from sticking to wrap.