Ingredients

5 ounces dark chocolate (3/4 cups), plus 2 ounces finely chopped dark chocolate (about 1/3 cup)
4 ounces unsalted butter, plus enough to grease the pan
1/2 cup cocoa powder
I used Valrhona
1 3/4 cups flour
1/2 teaspoons kosher salt
2 teaspoons baking soda
1 1/2 teaspoons baking powder
3 large eggs
1 1/4 cups granulated sugar
1/4 cup brown sugar, packed
2 teaspoons vanilla extract
1/2 cup sour cream

Ganache glaze
3 ounces dark chocolate (about 1/2 cup), chopped
1/2 tablespoon corn syrup
1/3 cup heavy cream

Directions

Preheat the oven to 325 and butter your pan.
Melt 5 ounces of chocolate and butter over a double boiler, add 1/2 cup water and the cocoa powder. Stir until cocoa is dissolved and set aside to cool.
Sift together the flour, salt, baking soda and baking powder.
In a stand mixer with the paddle attachment, beat the eggs a few seconds to combine, add the sugar and the brown sugar and whip until light and very thick (about 3-4 minutes). Add the vanilla and beat until the mixture forms a wide ribbon when the beater is lifted out.
Gently fold the chocolate mixture and sour cream into the eggs and sugar, and fold in the flour mixture in thirds. Pour half of the mixture into the pan and add the 2 ounces of finely chopped chocolate. Fill the pan, and bake for 50-60 minutes.
Cool about 30 minutes on a rack, and turn out of the pan.
In a small saucepan, bring the cream to a boil. In a heatproof bowl, combine 3 ounces of chopped chocolate with the corn syrup. Pour the hot cream over the chocolate and let stand until melted, about 5 minutes. Whisk until smooth. Let the ganache glaze cool until thick but still pourable, about 5 minutes.
Pour the ganache over the cooled cake. Let the cake stand until the glaze is set, at least 30 minutes, before serving.