Photograph: Chris Alack
Preheat the oven to 190°C, fan 170°C, gas 5. For the chocolate filling, bring the cream to the boil in a small pan. Put the chocolate in a bowl, pour over the hot cream and mix until shiny and combined. Fold in the orange zest. Chill for 2 hours until set yet spreadable. You can chill it for longer, but it will need to come back to room temperature to be spreadable.
For the cookies, beat the butter and sugars together with an electric whisk until light and fluffy. Add the beaten eggs a little at a time, whisking until combined. Stir in the vanilla extract.
Tip in the flour, bicarbonate of soda, baking powder and a pinch of salt. Mix until you have a clay-like dough.
Fold in the chopped chocolate. Take pieces of the dough (about the size of a tablespoon) and roll into balls to make about 30. Transfer to baking trays lined with baking paper, making sure the dough has plenty of room to spread out while cooking.
Bake in batches for 12-15 minutes until golden. Leave for 5 minutes before transferring to wire racks to cool completely.
Spread the filling over half of the cookies, then sandwich together with the remaining cookies.
Get ahead: make the cookies and filling up to a few days ahead; store the cookies in an airtight container and chill the filling. The cookies freeze well, too
Kitchen secret: you can bake the cookies from frozen. Freeze the formed cookies on trays until solid, then transfer to freezer bags. Bake on a tray for 15 minutes.