Preheat the oven to 180C/350F/Gas mark 4
Sift the flour and icing sugar into a bowl. Rub in the butter and cream cheese. Stir in the sour cream mix to a firm dough. Cover and refrigerate for 30 minutes.
Roll the dough between sheets of greaseproof paper to a rectangle about 25cm x 40cm. Spread evenly with the filling. Roll up the dough from each long side to meet in centre; cover. Refrigerate until firm.
Cut the roll into 5mm slices. Place the slices on greased baking trays about 2cm apart. Bake for about 20 minutes or until lightly browned. Stand for 5 minutes before lifting onto wire racks to cool. Dust half of each biscuit with sifted extra icing sugar.
Creamy Nut Filling: Beat the peanut butter, cream cheese, sifted icing sugar and water in small bowl until just combined.
