• Preheat the oven to 350℉ / 175℃. Prepare the cookie sheets with silicone mats or parchment paper, set aside.
• In a stand mixer fitted with a paddle attachment or a large bowl with a hand mixer, add ¾ cups Light brown sugar and 1½ cups Unsalted butter, softened. Beat until well mixed.
• Add 1½ tsp Vanilla extract, 3 large Egg yolks, and ¾ tsp Fine sea salt. Mix until combined.
• Gradually add in 3 cups All-purpose flour and mix.
• Using a 1 Tbsp cookie scoop or eyeball it, scoop some dough then roll it into a 1-inch / 2.5-cm ball. Repeat with the remaining dough.

Coating

• Take a dough ball and place it into the egg white mixture, using a fork gently roll the ball around then scoop it out. There may be egg white dripping down, just use the fork to take away the excess.
• Note: I recommend working with half of the nuts to begin with as the nuts will begin to get coated with egg white and get a bit sticky, making it harder to work with as time goes on. Once you're halfway through or use up most of the nuts, then add the remaining nuts so they're "fresh" for the remaining dough balls.

  Drop the dough ball into the chopped nuts and roll it around until evenly coated. Place onto a prepared cookie sheet.
• Make a thumbprint indentation on the top of each cookie then and add about ¼ tsp of jam to each cookie.
• Bake for 15 minutes or until slightly browned on the bottoms. Remove from the oven and cool completely.

Storage

• Place cookies into an air-tight container for up to a week. For long-term storage, place into the freezer for up to 3 months.