Preheat oven to 400°F (200°C). Whisk together flour, sugar, baking powder and salt. Cut butter into flour mixture using pastry-blender or fingertips until mixture resembles coarse meal. Stir in currants.
In small bowl, whisk together ¾ cup (175 mL) cream, egg, lemon zest and vanilla. Stir into flour mixture just until moistened (do not overwork dough). Transfer dough onto lightly floured board; pat into 7-in. (18-cm) round. Cut into 8 wedges. Place wedges 2-in. (5-cm) apart on parchment-lined baking sheet.
Brush tops lightly with cream; sprinkle each wedge with pinch of sugar. Bake 18 to 20 min., or until golden brown. Serve warm or at room temperature.
Substitute raisins or dried cranberries for currants.