INGREDIENTS
Unsalted butter, room temperature, for pans
3 cups
all-purpose flour, plus more for pans
3 cups
granulated sugar
1 1/2 cups
unsweetened Dutch-process cocoa powder
1
tablepoon baking soda
1 1/2 tsp
baking powder
Coarse salt
4
large eggs
1 1/2 cups
low-fat buttermilk
1/2 cup
plus 2 tablespoons safflower oil
2 tsp
pure vanilla extract
4 cups granulated sugar
1/4 cup light corn syrup
2 cups heavy cream
Coarse salt
2 sticks cold unsalted butter, cut into tablespoons
1/4 cup plus 2 tablespoons Dutch-process cocoa powder
2 sticks unsalted butter, room temperature
1/2 cup confectioners' sugar
Coarse salt
1 pound semisweet chocolate, chopped, melted, and cooled
Garnish: flaked sea salt, such as Maldon