Take the butter out of the fridge so it softens a bit.
In a large bowl, mix flour, salt and sugar. Make a mould.
Add butter, egg and egg yolks to the mould.
Knead the dough for few minutes until all ingredients combine.
Store the dough in the fridge for at least 1 hour.
Divide the dough into four equal parts and store the ones you won't use in the fridge. The raw cookies won't keep their shape if the dough gets too soft.
Prepare two baking sheets with parchment paper.
Preheat the oven to 180°C (350°F).
Sprinkle flour on the worktop.
Roll the dough to about 4-5mm thickness (1/5 inch).
Using a cookie cutter, cut the dough into shapes. Re-roll the remaining dough and continue cutting until all is used.
Repeat until you run out of dough.
Arrange cookies on the parchment paper of the baking sheet (2-3cm apart - 1 inch)
If you want your cookies to be golden or decorate them with sprinkles, whisk the egg yolk in a small bowl with a fork and brush them with this mixture. Then, use the sprinkles.
Bake for 8-10 minutes.
Let them cook on the baking sheet for a few minutes before transferring them into a tin.
