Place the butter in a medium saucepan and melt over medium heat, stirring often, until it foams, smells nutty, and browns. This will take about 5 to 7minutes. Scrape the browned butter into a medium bowl. Let cool to room temperature. You can place the butter in the fridge to speed up the process, just don’t let the butter become solid. You want it to be liquid, just cooled down.

In a medium bowl, whisk together the flour, baking soda, sea salt, and cinnamon. Set aside.

In the bowl of a stand mixer or with a hand mixer, beat the brown butter and sugars together until smooth, scraping down the sides of the bowl with a spatula as necessary.

Add the eggs and vanilla extract. Mix until combined.

Add the dry ingredients and mix on low until just combined. Don’t over mix. Stir in the oats.

Scoop the dough into balls, about 2 tablespoons of dough for each cookie.

Preheat the oven to 350 degrees F. Line a large baking sheet with parchment paper. Place the cookie dough balls on the prepared baking sheet, about 2-inches apart.

Bake for 10 to 12 minutes or until cookies are golden brown around the edges but still a little soft in the center.

Remove from the oven and immediately sprinkle with flaky sea salt. Let the cookies cool on the baking sheet for 5 minutes. When they are set up, transfer to a cooling rack to cool completely.