Preheat oven to 350 F. Lightly grease baking sheet. Bring currants and 4 Tbs orange juice to boil in small saucepan. Stir; remove from heat and cool. Combine flour and sugar in large bowl. Cut in butter until mixture resembles coarse meal. Stir in currant mixture and remaining 1 Tbs orange juice. Knead just until dough holds together. Roll dough out on prepared sheet into 10x12-inch rectangle. Trim edges and use scraps to square off corners. Prick entire surface with fork. Sprinkle with sugar. Cut into 24 squares, leaving in place on baking sheet. Bake until pale golden, 20 to 22 minutes. Recut while warm. Cool on rack. Store in airtight container.