Preheat the oven to 325 degrees F. Spray the insides of the ramekins with cooking spray. Distribute 1 tablespoon sugar among the 4 ramekins to coat.
In a medium bowl, beat the egg yolks and remaining 1/3 cup sugar with a handheld mixer until the yolks are pale yellow and the sugar dissolves. In a small bowl, combine the cocoa, flour, and salt. In another small bowl, combine the vanilla and milk. Add half the cocoa mixture to the eggs followed by half the milk mixture, beat until smooth, and then add the remaining cocoa and milk mixtures.
In a small, clean bowl with clean beaters, whip the egg whites until stiff. Using a rubber spatula, gently fold the egg whites into the chocolate mixture until incorporated. Be careful to not mix the air out of the egg whites. Divide among the ramekins. Place the ramekins in baking pan and carefully fill the pan with hot water until it reaches halfway up the sides of the ramekins. Bake until the cakes have risen and the centers spring back at a gentle touch, 15 to 17 minutes. Meanwhile, in a small bowl, mix together the sour cream and brown sugar and set aside.
When the puddings are done, remove from the water and serve with a dollop of sweetened sour cream and a sprinkle of orange zest. Serve warm.