Preheat the oven to 350 and line two sheet trays with parchment paper.
Place the butter in a small sauce pan over medium heat. Let the butter melt, and brown. Keep a close eye on it because it can burn really quickly. You will know it's nice and brown when the butter becomes foamy and aromatic. It will smell like toasted hazelnuts. As soon as it's golden brown pour the butter into a glass jar and let cool in the refrigerator for 20minutes.
In the bowl of a stand mixer beat together the brown sugar, vanilla and cooled brown butter for 2 minutes. Next add in the eggs one at a time. Mix on high for one minute. Last with the mixer on low slowly add in the dry ingredients.
With a small ice-cream scoop or a 1/4c measuring cup scoop the cookies onto the parchment lined baking sheet. Leave about 2 inches of space around each cookie so they have room to spread while they bake. Put the sheet tray with the cookies in the freezer or fridge for 15minutes before you bake them so that they don't spread too much.
Bake the cookies for 12 minutes. Let cool completely.