Pre-heat the oven to 180°C.
Sift the icing sugar, flour, and cornflour into a bowl and stir in the ground almonds.
Rub the cubed butter into the dry ingredients until no lumps remain and stir in the almond essence.
Knead the mixture briefly on a floured surface to form a smooth dough.
Roll dough into balls, place in a greased muffin tin, and flatten slightly.
Bake for 8 to 12 minutes until light gold, then make a small indentation in each top.
Cool for a few minutes before gently tapping the shortbreads out of the tin.
Dust with icing sugar and fill the indentations with jam once cooled.