In a bowl of a electric mixer, beat the butter and sugar until light and fluffy. Add the egg yolk and vanilla extract and beat until combined.
2
In a separate bowl, whisk together flour and salt. Add the flour mixture to the batter and beat just until combined. Refrigerate for about 30-60 minutes if the batter is too soft to roll.
3
Preheat the oven to 350 degrees.
4
In a small bowl, whisk the egg white until frothy. Place the chopped nuts on a plate and roll the dough into 1 inch balls. Taking one ball of dough at a time, dip first into the egg white and then lightly roll in the nuts. Using your thumb or end of a wooden spoon, make a indentation into the center of each cookie and fill with about 1/2 teaspoon of jam.
5
Bake for about 12-15minutes, or until cookies are set and the nuts have nicely browned. Remove from the oven and let it cool.
