3/4 cup dark unsweetened cocoa powder
1 & 1/4 cups hot water
2/3 cup sour cream
2 & 2/3 cups all-purpose flour
2 teaspoons baking powder
1 teaspoon baking soda
1/2 teaspoon salt
3/4 cup unsalted butter, softened
1/2 cup shortening
1 & 1/2 cups granulated sugar
1 cup firmly packed dark brown sugar
3 large eggs, at room temperature
1 tablespoon vanilla extract
1/2 cup heavy cream
1 teaspoon fleur de sel
1 cup granulated sugar
2 tablespoons light corn syrup
1/4 cup sour cream
1 pound dark chocolate (60-70% cacao), chopped
1 & 1/2 cups heavy cream
1 cup granulated sugar
2 tablespoons light corn syrup
2 cups unsalted butter, soft but cool, cut into 1/2-inch pieces
2 teaspoons fleur de sel, plus more for garnish