1-1/2 cups firmly packed light brown sugar
1 cup unsalted butter, melted and slightly cooled
2 large eggs
2 teaspoons vanilla extract
2 cups all-purpose flour
1 teaspoon baking powder
1 teaspoon kosher salt
1 (4-ounce) bar bittersweet chocolate, chopped and divided
1 cup chopped toasted pecans, divided
Vanilla ice cream, to serve
Preheat oven to 325°. Spray a 10-inch cast-iron skillet with baking spray with flour.
In a medium bowl, whisk together brown sugar and melted butter until smooth. Whisk in eggs and vanilla.
In a large bowl, whisk together flour, baking powder, and salt. Gradually add sugar mixture to flour mixture, stirring to combine. Stir in half of chocolate and 1/2 cup pecans. Spread batter into prepared pan.
Bake until a wooden pick inserted near edge comes out clean, top is golden brown, and center is set, about 30 minutes. Sprinkle with remaining chocolate and remaining 1/2 cup pecans. Let cool for 1 hour on a wire rack. Serve with ice cream.