Pistachio and chocolate ricciarelli

Line 2 large baking trays with baking parchment. Put the pistachios in the bowl of a food processor with 1 tbsp icing sugar. Whizz until finely ground, add the ground almonds and pulse to combine. Tip the egg whites into a medium sized bowl, add a pinch of salt and the lemon juice; whisk until they just hold stiff peaks. Sift 210g icing sugar and the baking powder into the bowl, add the ground pistachio and almond mixture, lemon zest, almond extract and vanilla and fold in using a large metal spoon.

Continue mixing until thoroughly combined. Using slightly damp hands, divide the mixture into 20 even walnut-sized balls. Press a small chunk of chocolate into the middle of each ball and mould the mixture around to seal. Tip the remaining 75g icing sugar into a bowl or tray and roll each ball in the sugar to coat thoroughly, thickly and evenly. Arrange over the lined baking trays and leave uncovered at room temperature for 30 minutes. This resting and drying allows a thin crust to form on the surface of the ricciarelli.

Preheat the oven to 150 degrees C, gas mark 2. Bake the ricciarelli for 30-35 minutes, turning the trays around if needed, until the biscuits are just firm and starting to turn golden at the edges. Cool completely before packing into pretty boxes or bags.