Step by step recipe:

1. 10 min.
   Start by roast 125 g walnut kernels: put on a baking sheet and put in the oven at 300°F (150°C) for 10 minutes.
   
   Walnut should dry without coloring.
2. 3 min.
   Let cool, then mix to get a powder.
3. 3 min.
   In a food processor bowl, pour 125 g butter and 125 g icing sugar, start at low speed and kneed until homogeneous mixture.
4. 5 min.
   Add 250 g flour and 1 egg, and continue to kneed until homogeneous mixture.
5. 5 min.
   Make a kind of ball with the dough.
6. 2 hours
   And put it between 2 plastic film sheets to make a kind of thick circle. Put in the fridge for at least 2 hours or a night, otherwise 30 minutes in the freezer.
   
   We do that because dough is very very soft at ambient temperature.
7. 10 min.
   Preheat your oven at 360°F (180°C).
   
   Spread the dough, not too thin, on the working surface, and cut in circles...
8. 
   ...that you lay on a baking sheet.
9. 
   You can also make square shapes using a roll.
10. 25 min.
    Put in the oven and make cook for about 25 minutes, watch for color because short bread should not be too cooked otherwise they are dry.
    
    Let cool on a wire rack.