For the biscuits:
1) In a large bowl, beat the butter, caster sugar, vanilla, cinnamon, and salt with an electric mixer until light and fluffy, about two minutes. Beat in the egg. Stir in the plain flour until just blended. Mix in the apricots, almonds, and pine nuts.
2) Transfer the dough to a sheet of clingfilm and shape into a log, about 30cm long and 4cm in diameter. Wrap the dough in the plastic and refrigerate for two hours.
3) Preheat the oven to 180°C / gas mark 4. Line two heavy baking sheets with parchment paper.
4) Cut the dough log crosswise into 1/2 to 1cm thick slices. Transfer the biscuits to the prepared baking sheets, spacing evenly apart. Bake until the cookies are golden around the edges, about 15 mins. Transfer the biscuits to a wire rack to cool completely before icing.
For the icing:
1) Place the icing sugar in a medium mixing bowl. Gradually whisk in the almond flavored liqueur, until the mixture is of drizzling consistency.
2) Place the wire rack over a baking sheet. Using a spoon or fork, drizzle the biscuits with the icing, allowing any excess icing to drip onto the baking sheet. Allow the icing to set before serving, about 30 mins.