1. Preheat oven to 400 degrees. Line a baking pan with a Silpat or parchment paper. Sift flour and baking powder into a medium bowl. Rub butter and sugar into flour to form a fine crumble. Make a well in center, and add milk and currants, if using. Knead gently together, being careful not to overmix. (Dough will be sticky.)

2. On a generously floured surface, roll out dough to 3/4-inch thickness. Stamp out eight 2 1/2-inch rounds with a plain pastry cutter. Transfer to prepared pan, and brush tops with egg yolk. Allow to stand for 15 minutes.

3. Bake until risen and lightly golden on top, 12 to 15 minutes. Remove to a rack to cool. Serve warm with clotted cream and strawberry jam.