Preheat oven 350°F (177°C).
In a small bowl, whisk egg yolks and vanilla extract. Set aside.
In large mixing bowl with paddle attachment, or using an electric hand-held mixer, beat the butter and sugar until fluffy, about 2 minutes.
Add the egg yolk mixture and continue mixing until well combined, scraping down the sides couple times.
Stir in flour, baking powder and salt. Mix just until well combined.
Add nuts and chocolate chips, if desired.
Using a medium cookie scoop, form into 1.5-inch balls and place them on baking sheets with plenty of space to spread. Flatten the dough slightly before baking.
Bake for 8-10 minutes, or until the edges are set.