Hot Fudge Sauce
2/3 cup heavy cream 1/2 cup light corn syrup 1/3 cup packed dark brown sugar 1/4 cup unsweetened Dutch-process cocoa powder 1/4 teaspoon salt 6 oz fine-quality bittersweet chocolate (not unsweetened), finely chopped 2 tablespoons unsalted butter 1 teaspoon vanilla Bring cream, corn syrup, sugar, cocoa, salt, and half of chocolate to a boil in…