Mix the flour and icing sugar in a bowl.
Rub the butter into the flour and sugar until it starts to form together in a dough.
Wrap the dough in clingfilm and place in the fridge to rest for 30-60 minutes. Pre-heat the oven to 170 degrees C (150 degrees C for fan ovens).
Roll the dough out to approximately 1 1/2 cm thick.
Using a knife, cut the shortbread into 9-12 small rectangles.
Place the shortbread onto a baking tray lined with baking paper.
Brush the top of the shortbread with a small amount of milk.
Add flaked almonds to the top of the shortbread (you may need to press these down a little).
Bake in the oven for between 15 and 20 minutes (until pale golden in colour).
Remove from the oven and allow to cool on a wire tray for approximately 30 minutes.