In a small saucepan over medium heat melt and brown your butter. A good trick is once the butter stops making popping sounds, it is done and should be immediately taken off the heat.
Combine the hot butter, brown sugar, and granulated sugar in a large mixing bowl. Mix until combined with a wooden spoon.
Add the vanilla and eggs, stir until combined.
Add the dry ingredients: flour, salt & cream of tartar. Mix until the dough forms.
Pour the chocolate chips into the mixture and fold in
Spread the batter out onto a sprayed and parchment paper lined 9x13 pan
Bake for 30 minutes.
Remove and allow to cool for 10 minutes before slicing.