Double Chocolate Brownie Cakes

1 cup plus 2 tablespoons unsalted butter, plus more for greasing

1 1/2 cups chopped milk chocolate bar(about 9 ounces), divided

3/4 cup (2 1/2 ounces) unsweetened cocoa

1/2 cup (about 2 1/8 ounces) all-purpose flour

4 1/2 tablespoons (about 1 1/4 ounces) cake flour

3/4 teaspoon kosher salt

3 large eggs

1 cup plus 2 tablespoons granulated sugar

3/4 teaspoon vanilla extract

Vanilla ice cream, for serving

Preheat oven to 350°F. Grease a 12-cup muffin tray; set aside. Melt butter in a small saucepan over medium. Remove from heat, and add 1 1/2 tablespoons chocolate; whisk until melted. Let cool slightly, about 6 minutes.

Meanwhile, whisk together cocoa, all-purpose flour, cake flour, and salt in a small bowl; set aside. Beat eggs and sugar in a large bowl with an electric hand mixer on medium speed until pale and thick, about 5 minutes. Add vanilla, and beat until incorporated. Add flour mixture in 3 additions alternately with butter mixture, beginning and ending with flour mixture and beating until just combined after each addition. Stir in remaining chopped chocolate.

Spoon batter into prepared muffin tray, about 1/3 cup per well. Bake until cakes rise and spring back when lightly touched, about 20 minutes. Let cool in muffin tray on a wire rack for 15 minutes. Serve warm with vanilla ice cream.