In a pan, melt together the margarine, sugar and golden syrup together. Add in the spices, flour and bicarbonate and mix together. If a little dry, add in a little extra water to bind. Chill for 2 hours then roll out the dough between 2 sheets of baking paper, cut into rounds and use to line the bases of mini muffin tins. Fill each with a spoonful of mincemeat and cut out gingerbread pastry stars and stick on top. Bake in the oven at 200°C for 15-20 minutes, remove from the oven and let it cool down completely. Meanwhile, make the buttercream  by beating together the butter, icing sugar and alcohol for 6-8 minutes or until light and fluffy. Place into a piping bag fitted with a large star nozzle and pipe a buttercream kiss on the top of each mince pie.