Preheat oven to 375 degrees F. Lightly coat 2 5-inch cast iron skillets with nonstick spray.

In a large bowl, combine flour, baking soda and salt; set aside.

Melt 10 tablespoons butter in a medium saucepan over medium heat. Cook, whisking constantly, until the foam subsides and the butter begins to turn a golden brown, about 3 minutes. Remove from heat; strain through cheesecloth or fine sieve.

Stir in remaining 4 tablespoons butter until completely melted. Whisk in sugars and vanilla until well combined. Whisk in egg and egg yolk until well combined. Add flour mixture, beating just until incorporated. Gently fold in chocolate chips.

Divide mixture into the prepared skillets. Place into oven and bake until edges are golden brown but center is still moist, about 12-15 minutes.

Serve immediately, topped with ice cream, if desired.