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. Cover and place in the fridge until the butter sets up. It should be soft but not solid. This should take about 30 to 45 minutes.
Preheat oven to 350 degrees F. Line a large baking sheet with parchment paper or a Silpat baking mat.
In a medium bowl, whisk together flour, baking soda, and sea salt. Set aside.
In the bowl of a stand mixer, beat together the chilled brown butter, brown sugar, and granulated sugar until smooth. Add the eggs and vanilla and mix until combined.
Add the dry ingredients and mix on low until just combined, don’t over mix.
Stir in the chocolate chips and chopped Twix candy bars.
Roll the cookie dough into balls, about 2 tablespoons of dough per cookie. Place the 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 sprinkle the cookies with flaky sea salt. Let cool on the baking sheet for 5 minutes and then transfer to a cooling rack to cool completely.
You can chill the dough for up to 72 hours and then bake the cookies.