Preheat oven to 350°. In a 12-inch cast-iron skillet, place 2 tablespoons butter. Place skillet in oven to preheat.
In a small saucepan, melt remaining 1 cup butter and unsweetened chocolate over medium-low heat, stirring until smooth. Let cool slightly.
In a large bowl, beat sugars, eggs, and vanilla at medium-high speed with a mixer until fluffy and pale. Reduce speed to medium-low; gradually beat in flour and salt until combined. Stir in melted chocolate mixture until smooth. Stir in butterscotch, chocolate morsels, and pecans. Carefully remove skillet from oven; spoon batter into skillet.
Bake until center is set, 35 to 40 minutes. Let cool 30 minutes. Serve with ice cream.
Recipe by Southern Cast Iron at https://southerncastiron.com/chocolate-butterscotch-skillet-brownies/