Add the butter, sugar and salt to a bowl. Knead it through with your hands to a homogenous mass. This will prevent butter clumps in your dough later on.
350 g unsalted butter, 250 g granulated sugar, 1 pinch salt
Now add the flour, hazelnut and egg yolk. Knead until combined and then roll it into a big ball..Cover the cookie dough with clingfilm and leave it to rest in the fridge for at least 30 minutes. This will allow the butter to cool down again and make the dough easier to shape.
500 g flour, 150 g ground hazelnut, 1 egg yolk
Preheat your oven to 180°C or 356°F, top to bottom heat.
Divide the dough into two portions and then roll it out to approx. 3 mm thick.
Using cookie cutter of your choice, cut out equal amounts of top and bottom cookies. For the tops, if you don't have a "Linzer cookie cutter", use a smaller cookie cutter or a round tip of your piping bag to make a hole in the middle.
Place the cookies on a try lined with baking paper. Always make one tray with tops, and one tray with bottom cookies.
Bake for around 6-10 minutes. The cookies should be golden brown, and not get too dark.
Should your jam be difficult to spread, you can heat it up in a saucepan a little to make it more liquid. If you are using a jam with bits, strain the jam through a sieve.
You can either spread the jam with a spoon, or, my preferred method is to fill the jam in a piping bag, cut a hole at the small end, and pipe it onto the bottom biscuits. Leave a 2-3 mm edge free when adding the jam, otherwise, it will squeeze out the sides.
1 jar jam
Sprinkled the top biscuits with icing sugar before placing them onto the bottom biscuits.
100 g icing sugar /confectioners sugar
Serve immediately or place in a cookie tin until needed.