Make brown butter with one of the butter cubes. Let cool briefly.
In bowl of stand mixer combine brown and white sugars, brown butter and remaining cube of butter. Mix until well combined.
Scrape sides of bowl. Add eggs and vanilla extract and mix on medium high speed to whip until fluffy.
To the bowl add the flour, baking soda, salt, chocolate chips and Heath Bar bits if using. Mix on low just until dough comes together.
Refrigerate covered dough for two hours and up to three days before baking. This is one of the great secrets to enhancing the flavor of your cookies!
Preheat oven to 350F.
When ready to bake cookies remove dough from refrigerator 30-60 minutes before baking. Dough should still be firm to the touch but not cold when ready to bake.
Bake cookies at 350F for 8-10 minutes. Remove from oven and cool slightly on sheet pan before transferring to a wire rack to finish cooling.
Enjoy!