Preheat your oven to 350F.
Over medium heat, brown your butter. Refer to "how to brown butter" above if you're unsure how to do this.
Transfer butter to a bowl and place in the freezer for 5-10 minutes to cool to room temperature.
While the butter is cooling, add your flour to a baking sheet lined with parchment paper. Place the flour into the oven for 4-5 minutes. Be sure to check your flour very minute to make sure it's not burning.
Once your flour is out of the oven, pour it into a medium mixing bowl. To the same bowl, add brown sugar, granulated sugar, and salt. Mix until combined.
Once your butter has cooled, add it to the mixing bowl along with your milk and vanilla. Mix until the dough has come together. If it still feels dry, you can add more milk 1/2 teaspoon at a time.
Use a rubber spatula to fold in chocolate chips if using them. Enjoy!