Preheat the oven to 180°C and line 2 baking trays with baking paper.
In a large bowl combine the butter and 1 cup of icing sugar.
Add in the flour, corn flour and vanilla and mix with your hands until well combined.
Knead together the mixture to form a soft dough.
Cover the dough with plastic wrap and allow it to stand for 10 to 15 minutes.
Turn the dough out onto a floured counter and roll out to about 1/2 cm thick.
Cut out the cookies with a round cookie cutter and place them on the lined baking tray.
Bake for about 10 – 12 minutes, remove from the oven and let them cool on a rack for 10 minutes.
Once completely cool, spread half the biscuits with dulce de leche and gently sandwich the biscuits together.
Sprinkle them with icing sugar and enjoy!