easy small cake with walnuts

ingredients:
220 grams of butter
120g icing sugar
2 yolk
2 egg whites
360 grams of flour
40g walnuts finely ground (powdered if possible)
4 pinches baking powder
160g chopped walnuts
1 coffee spoon of vanilla
method:

Beat butter and sugar with an electric mixer for 5 minutes.
Add egg yolks and vanilla and beat for 1 minute.
Add the flour and baking powder and mix with your hands to scoop the batter.
Put it in the fridge for 30 minutes.
Remove the dough from the fridge and make 32 balls.
move them into the egg white, lightly beaten then in crushed nuts.
Make a hole in the center of the balls with a finger.
Transfer to a baking tray and bake at 180 degrees for 20 minutes.
Remove from oven and let cool.
Fill the holes with a small coffee spoon of strawberry jam.
http://www.bonoise-recettes.com/277-index.html