Preheat oven to 175°C and line 4 cookie trays with baking paper.
Place sugar into the Thermomix bowl and mill 10 sec/speed 10. Add butter and chop 10 sec/speed 6 or until combined.
Insert Butterfly and whip 1 min/Butterfly/speed 3 scraping sides of bowl as needed.
Add egg yolks, one at a time, while mixing 30 sec/Butterfly/speed 3. Remove Butterfly.
Add remaining ingredients, except for the flour and combine 10 sec/speed 5. Scrape down sides of bowl and add flour. Combine 20 sec/Interval bringing together with spatula until combined.
Wrap up cookie dough in a floured silpat mat and refrigerate for at least 30 minutes.
Place walnut sized balls of dough onto the baking trays, leaving room for spreading. Sprinkle with a few scant flakes of salt. Bake for 8-10 minutes or until browning on edges.