Preheat oven to 375 degrees F. Drain currants and pat dry. Into a large bowl sift together flour, sugar, baking powder and salt. Add butter and blend with a pastry blender or your fingertips until it forms fine crumbs. Add currants and mix well.
Add half-and-half, and stir with a fork just until it comes together and forms a dough. Turn out onto lightly floured work surface and knead for 1 minute. Roll out into a 3/4-inch thick round. Use a lightly floured 3-inch cookie or biscuit cutter to stamp out rounds. Pat together scraps and reroll. Place on a greased cookie sheet and brush tops with egg glaze. Bake for 25 to 30 minutes, until puffed and golden brown.