Photo: Chris Alack
Preheat the oven to 190°C/fan 170°C/gas mark 5. 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.
Beat the butter and sugar 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 and roll into balls. 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 the cookies, then sandwich together with the remaining cookies.