Currant-studded scones are wonderful warm from the oven -- and easy enough to make for a weekend breakfast.
Whisk flour, granulated sugar, baking powder, baking soda, and salt in a large bowl. Using a pastry blender, cut in butter until mixture forms coarse crumbs with a few large clumps. Fold in currants.
Make a well in center of flour mixture; pour in 2 cups cream. Using your hands, draw dry ingredients over cream, gradually gathering and combining the dough until it just comes together. If it is too dry, add more cream, 1 tablespoon at a time.
Turn out dough onto a lightly floured work surface. With lightly floured hands, gently pat dough into a 7-by-11-inch rectangle, about 1 inch thick. Using a sharp knife, cut the rectangle into 16 triangles. Transfer triangles to baking sheets lined with parchment paper; cover with plastic wrap, and freeze until very firm, at least 2 hours or overnight.
Preheat oven to 375 degrees. Lightly beat egg yolk with remaining 1/4 cup cream in a small bowl; brush over tops of scones. Sprinkle generously with sanding sugar, if desired. Bake until golden and flecked with brown spots, 30 to 35 minutes. Transfer scones to a wire rack. Serve warm or at room temperature. Scones are best eaten the day they are baked.