Line a large baking tray with baking parchment and set aside. Whisk the cocoa, caster sugar, oil and egg together in a bowl until smooth. Sieve over the flour, baking powder and a small pinch of salt, then mix well to make a soft dough. Wrap and chill for 1 hr to firm up slightly.

Heat the oven to 190C/170C fan/gas 5. Sieve the icing sugar into a shallow bowl. Roll the chilled dough into 15 even-sized balls (about 20g each) using your hands. Roll the dough balls in the icing sugar, then arrange on the prepared baking tray, evenly spaced apart. Bake for 9 mins, then press an Easter chocolate into the middle of each cookie, alternating the flavours, and bake for 1 min more. Leave to cool completely on the tray – the cookies will firm up more as they cool. Will keep in an airtight container for up to three days.