Preheat the oven to 400°F Plump the currants in the orange juice. Sift the dry ingredients together. Cut the butter into small pieces and cut it into the dry ingredients using a pastry blender or 2 knives until it resembles coarse meal. Add the currants and juice.
Stir the zest into the buttermilk, add it to the dry ingredients, and stir until the mixture is moistened.You may need to add a little more buttermilk. Do not overmix.
Turn the dough out onto a floured board and gently form into a round about 1 inch high. Cut the round into 8 wedges and place 1 inch apart on a baking sheet stacked on top of another sheet. (The double pan is necessary to keep the bottoms from browning too quickly.) Whisk the egg yolk and milk together and lightly brush the scones with the mixture. Sprinkle with the pecans. Bake until the scones are ligthly browned, about 20 minutes.
VARIATION: Apricot-Walnut Scones: Chop 1/2 cup dried apricots into small pieces and use them in place of the currants. Plump the apricots in the orange juice and prepare the scones as directed, substituting walnuts for the pecans.