1. Preheat the oven to 180 °C and line a baking tray with baking paper.
2. Beat the butter and Zùsto together in a bowl until light and fluffy.
3. Add the eggs one at a time, making sure to beat the mixture well after each egg until they are fully incorporated. Then add the vanilla extract and mix well.
4. Sift the flour and salt over the butter-sugar mixture. Gently fold it all together until everything is fully incorporated and you end up with a smooth dough.
5. Scoop the dough into a piping bag with a smooth nozzle.
6. Pipe strips of dough lengthwise onto the baking tray, making sure they are approx. 5 cm long and 2 cm wide. Make sure to leave enough space between each strip.
7. Bake the cats tongues in the preheated oven for 8-10 minutes, or until the edges turn a light golden brown color.
8. Remove the cats tongues from the oven and leave them to cool briefly on the baking tray before carefully transferring them to a wire rack to cool completely.
9. Store the cooled cats tongues in an airtight container.

Enjoy!