Pre-heat the oven to 150 deg C

Caramel: Set the oven to 220 deg C. This caramel needs to be made a couple of hours ahead. Empty the tin of milk into a pot or oven proof container and put a piece of foil on top. Put the pot or the container into a water bath where the water comes half way up the side of the pot you are using. Put into the oven and leave for an hour and a half. The milk will turn a caramel colour. Cool

Put the flour, corn flour, baking powder and pure sugar into a food processor and blitz. Add the chilled butter and whizz till it looks like buttery crumbs. Mix the vanilla and the egg and pour into the food processor while it is mixing. Mix till it is combined and gathers into a ball.

Roll the dough between two pieces of paper till evenly spread to about 1 cm thick. Put onto a tray and chill till very cold.

Cut out circles with a cutter ( the size you like) and put onto a lined flat tray

Bake at 150 deg C for 10-12 minutes. Make sure they don't colour because these should be snowy white biscuits.

Fill a small piping bag with cold caramel or spread the caramel thickly and sandwich two biscuits together. Sprinkle with icing sugar, store in an airtight container if there are any left. Some people prefer them the next day as they soften.