Preheat oven to 350°F. Line 2 cookie sheets with parchment paper.
Cream together butter and sugar in a stand mixer or with an electric hand mixer, until light and fluffy (about 2-3 minutes). Add eggs yolks, beating.
Slowly add the quick bread mix in batches, until the dough just comes together (scrape down the sides of the bowl as necessary). If using mix-ins, gently stir them in after the dough is fully mixed.
Drop dough by rounded tablespoonfuls on the prepared cookie sheets, leaving a couple of inches in between each cookie.
Bake for approximately 15-20 minutes (begin checking them around 12 minutes). Remove from oven and let cool on cookie sheets for 2 minutes, then move them to wire racks to cool completely.
