Brown the butter in a heavy-bottom medium saucepan over medium-low heat. When the butter has browned (about 3 minutes), set aside to cool. *If you don’t set the butter aside to cool, the chocolate chips will melt as you’re stirring them like mine did. And that is definitely not a problem. It just depends if you mind having chocolate swirls instead of chips in your cookies. In a medium sized bowl, sift together the flour, salt, and baking soda. Set aside the flour mixture.
In a medium sized bowl, mix the granulated sugar and molasses until no large molasses clumps remain.
Pour browned butter in the mixer’s work bowl. Add the homemade brown sugar. Cream the butter and sugar on medium speed for about 3 minutes. Add the egg and mix well. Add the yolk and mix until well combined. Slowly spoon in the flour mixture until thoroughly combined. Stir in the chocolate chips.
Chill the dough for about 20 minutes, then scoop onto parchment-lined baking sheets.
Bake for 8 to 10 minutes or until golden brown, checking the cookies after 5 minutes. Rotate the baking sheet for even browning. Cool completely and store in an airtight container.