Browning your butter

1. Brown butter over medium heat (approximately 8-12 minutes). Stir occasionally and watch as the butter begins to foam and becomes golden brown. Monitor closely to avoid any burning. Once it smells nutty and becomes amber in color, remove it from the stovetop.
2. Pour your browned butter into a heat-resistant container and place it on the countertop. Set a timer to let it cool for 20 minutes while you move ahead with this recipe. When you next use the butter, it’ll still be slightly warm but should not be so hot that you can’t touch it.

Baking your cookies

1. Preheat your oven to 350°F and start measuring out all your ingredients besides your brown butter, which should be cooling on the counter.
2. If using chocolate bars instead of chips, roughly chop them into small pieces and set aside. 
3. In a large mixing bowl or the bowl of a stand mixer, combine the cooled brown butter, white sugar, brown sugar, vanilla, salt, nutmeg, baking powder, and baking soda. Mix for about 90 seconds, scraping the bowl's sides halfway through the process to ensure your ingredients are incorporated. 
4. Pause mixing to add your egg yolk and incorporate it into wet ingredients for about 30 seconds.
5. Pour in flour and mix with a spatula until it’s evenly distributed in the dough.
6. Fold in your chocolate chunks or chips. 
7. Scoop golf-ball sized portions of your cookie dough onto ungreased aluminum baking sheets, with about 2 inches between each of them. Bake for 12 minutes. Transfer them to cooling racks after they’ve sat on the baking sheets 5 or so minutes outside of the oven and are firm enough to handle.