Line a 9 x 9 inch pan with nonstick foil or plain foil sprayed with nonstick spray and set aside.
Preheat the oven to 350°F (175°C).
In a microwave-safe bowl, combine 6 ounces chopped semi-sweet chocolate and the 11 tablespoons butter; microwave in 30-second intervals, stirring between each, until fully melted and smooth. Let cool 5–10 minutes.
In a large bowl, whisk together the sugar, eggs, vanilla, and a dash of salt until blended.
Whisk the cooled chocolate-butter mixture into the egg mixture until combined.
Gently stir in the flour until just incorporated; do not overmix.
Pour the batter into the prepared pan and spread evenly. Bake 26–28 minutes, or until a tester inserted into the center comes out with moist crumbs.
Cool the brownies completely on a rack before glazing.
To make the ganache, microwave the 1/2 cup cream until it just starts to boil. Pour the hot cream over the remaining 6 ounces of chocolate and let sit 5 minutes, then whisk until smooth and glossy.
Pour the ganache over the cooled brownies and spread to cover. Allow the topping to set, about 4 hours, then lift the brownies from the pan using the foil and cut to serve.