Place chopped couverture in a mixing bowl or saucepan.
Heat the advocaat in a small saucepan (do not boil!)
Pour the hot advocaat egg liqueur over the couverture.
Let the mixture steep for 2 minutes and then whisk until smooth. Cover the bowl with cling film and chill in the fridge for about 8 hours.
Making the Linzer cookie dough
Rub the flour, powdered sugar, and butter together with your fingertips until you get a crumbly mass (about 10 minutes).
Add the yolk and knead the whole mass with the food processor into a smooth dough (about 3 minutes).
Wrap the unbaked dough in plastic wrap and refrigerate for about 1 hour. Preheat the oven to 356 °F / 180 °C and cover two baking sheets with baking paper.
Roll out the dough on a floured work surface (about 0.12 inch in thickness) and cut out cookies. Make sure that you have the same number of solid cookies (without a hole) as cookies with holes.
Place the cut-out cookies on the baking sheet lined with parchment paper. Knead the excess dough that you have left again, roll it out, and make more cookies until there is no more dough left.
Bake the cookie-filled baking sheets one at a time in the oven on the center rack until golden brown (about ten minutes). After baking, remove the baked cookies from the baking sheet and let them cool.
Assembling the Cookies
Place the cookie bottoms on a sheet of baking paper.
Take the well-chilled egg liqueur ganache from the fridge and whip it birefly until it becomes spreadable! Important: Whip only briefly! If it is whipped too long with the mixer, it will flocculate!
Fill the cream into a piping bag and pipe small dots onto the cookie bases. Place the upper part of the cookie on top and press down lightly.
Sprinkle the cookie sandwiches with powdered sugar and place them in a storage container in a cool place.
Linzer Cookies with Jam
If you fancy filling your gorgeous cookies with jam, you have a wide range of filling opportunities. One of the best jams for Linz cookies is raspberry jam. The slightly tart flavor combines wonderfully with the sweet cookies. This also applies to apricot or currant jam. If you prefer it sweeter, you should choose strawberry jam.For those who like it exotic, I recommend trying these cookies with orange, quince, or mango jam!As you can see, there's no limit to the different combinations you can make here!Have fun experimenting!