Brown the butter: For a detailed tutorial, see this post on how to brown butter. Set aside & cool for 10-15 minutes while you prepare the rest of the cookies. 8 Tbsp. unsalted butter
Preheat the oven to 375°F and line 2 baking sheets with silicone baking mats or parchment paper.
Whisk together the dry ingredients in a medium sized mixing bowl: flour, cake flour, oats, cornstarch, baking soda, baking powder and salt. Set aside.
1 cup all purpose flour, 3/4 cup cake flour, 1/2 cup rolled oats, 1 tsp. cornstarch, 1/2 tsp. baking soda, 1/2 tsp. baking powder, 1/2 tsp. salt
Whisk together the brown sugar, granulated sugar and slightly cooled brown butter in another medium sized mixing bowl. Then whisk in the eggs, one at a time, and vanilla extract until combined.
1/2 cup dark brown sugar, packed, 1/4 cup granulated sugar, 2 large eggs, room temperature, 1 Tbsp. vanilla extract (yes, a tablespoon!)
Fold in the flour mixture.
Add in the butterscotch chips and mini chocolate chips and combine.
3/4 cup butterscotch chips, 1/2 cup mini chocolate chips
Use a cookie scoop to scoop cookie dough onto prepared baking sheets. (You should have ~10-12 cookies). The dough may be a little sticky at first but not too difficult to work with.
Bake in the preheated oven for 9-11 minutes or until the edges are slightly golden brown and the centers look done but still gooey. Remove from the oven.
Sprinkle the tops with flaky sea salt and garnish with more butterscotch chips or chocolate chips if desired. ENJOY!
garnish: flaky sea salt