Heat the oven to 160°C (140° fan) gas 3. Line a large baking tray with non-stick baking paper.
Melt the chocolate with the butter in a heatproof bowl over a pan of simmering (not boiling) water.
Beat the eggs and sugar until creamy and beat in the chocolate butter mixture.
Mix together the flour, baking powder and salt.
Fold the dry ingredients into the chocolate mixture and add the ground hazelnuts.
Place teaspoonfuls of the mixture on the baking tray and make a slight indentation in the middle of each. Bake for about 8 minutes until firm. Cool on the baking trays for a few minutes, then place on a wire rack to cool completely.
Beat the soured cream until smooth with half the icing sugar. 8 Whisk the cream until thick, with 1 tsp icing sugar. Fold the whipped cream into the soured cream and sweeten with the remaining icing sugar if desired.
Place a little cream in the centre of each cookie and chill for at least 30 minutes. 1
Melt the hazelnut spread with the palm oil, as before and spread thinly over the cream on each cookie. Leave to set.
Tips: Will keep 2-3 days if chilled.