Preheat the oven to 325 F with a rack in the center of the oven. Line a large baking sheet with parchment paper.

In a large bowl add the flour, baking powder, cardamom, brown sugar, and orange zest - mix it together well, using your hands to break up any brown sugar lumps.

Stir in the beaten eggs. Using your hands, bring the dough together until no floury bits remain. Work in the dried currants and walnuts until everything is evenly distributed.

Divide the dough into two pieces.

Lightly flour a clean non-stick surface for shaping. Shape each piece of dough into a 10 inch log. Carefully set the dough on the parchment lined baking sheet, spaced far apart. Bake for 30 minutes.

Remove the pans from the oven and allow them to cool slightly.

Transfer the biscotti logs to a cutting board and use a sharp knife to cut them into diagonal slices about ½" thick. Lie the slices flat on the baking sheet.

Reduce the oven temperature to 250 F and return the baking tray full of biscotti slices back to the oven.

Bake for another 20 minutes.

Turn them over, then bake for another 20 minutes. The thimblets should be dry and crunchy all the way through.

Serve with hot coffee or tea.