Preheat oven to 450 degrees. Lightly grease heavy large cookie sheet. Sift flour and baking powder into medium bowl. Mix in sugar. Add butter and rub with fingertips until mixture resembles fine meal. Whisk milk, whipping cream and egg yolk in small bowl to blend. Add to dry ingredients and stir just until combined. Mix in currants. Turn dough out onto floured work surface. Press to thickness of 1 inch. Cut out rounds using 2- to 2-1/2-inch cookie cutter. Gather scraps and press together to thickness of 1 inch. Cut out additional rounds. Transfer founds to prepared cookie sheet, spacing evenly. Brush with glaze. Bake until golden brown, about 15 minutes. Transfer scones to rack to cool slightly. Serve warm with butter and jam.