In a stand mixer, beat together butter, sugar, salt and vanilla for 2 minutes on medium speed, scraping bowl occasionally.
Press cooked egg yolks through a fine sieve with the back of a spoon into the mixing bowl and beat 2 minutes more, ensuring that the yolks are fully incorporated.
Stir flours to blend, then add to batter with hazelnuts and cherries. Mix lightly only to incorporate, do not over mix.
Form dough into 2-inch logs; wrap and place on a flat pan or plate and refrigerate overnight.
For more flavourful cookies, you can also roll the logs in chopped nuts before refrigerating, if desired.
The next day, when ready to bake, heat the oven to 350 F
Remove dough from the fridge and slice into 1/2-in slices and place on a prepared baking sheet, sprinkle with decorating sugar and dock holes in each cookie with a skewer or fork to release steam.
Bake 16-22 minutes until lightly browned. Cool and store in an airtight container or freeze.