Method

• 1.
  For the dough, place butter, icing sugar and vanilla in a stand mixer fitted with the paddle attachment and beat on medium speed until pale and fluffy. Whisk the flour, cornflour and 1/2 tsp fine salt in a medium bowl to combine and add to the butter mixture. Mix on low speed until dough comes together. Scrape onto a piece of plastic wrap and squeeze into a fat, flat disc, ensuring there are no buttery streaks left in the dough. Chill for a minimum of 2 hours, or overnight. When ready to roll, grease a large baking tray and line with baking paper.
• 2.
  Remove dough from fridge and allow it to soften a little at room temperature to become malleable (it will crack if you roll from cold). Roll on a lightly floured surface to 4mm thick. Chill for 20 minutes. Stamp out 16 large cookies and place on prepared tray (you can re-roll dough as many times as you need). Using smaller cutter, cut out ‘windows’ from 8 cookies. Chill for 30 minutes.
• 3.
  Preheat oven to 160°C/140ºC fan-forced. Bake for 25 minutes. Cookies will be pale but will have lost the raw shininess and look matte and cooked. Turn oven off and leave in oven, with door closed, to cool down slowly and make the cookies a little firmer.
• 4.
  Dust window cookies with icing sugar and set aside. Turn base cookies bottom-side up and carefully spread each with 1 tbs jam. Working with one cookie top at a time, lift a window cookie off tray by its sides and give it a light tap to dislodge any excess sugar.
• 5.
  Place it onto its jammy base. Once all cookies are paired, re-warm jam and use a heaped tsp of jam to carefully fill up the jam window. For a smooth jam finish, microwave jam in a small heatproof bowl on high for 30-seconds-1 minute or until runny. While warm, strain through a fine sieve set over a small bowl and discard any solids. This will give your cookie ‘windows’ a glassy sheen.