Combine milk, rolled oats and 2 tablespoons of the brown sugar in a large saucepan and mix well. Bring to a boil over medium heat, and continue to cook, stirring constantly, for one minute. Spoon one cup of the oatmeal into each of four augratin dishes or ovenproof bowls. Press the oatmeal down with the back of a spoon to spread it evenly in the dish. Top each serving with 1/4 cup of the yogurt, spreading it evenly over the entire surface. Arrange sliced banana rounds evenly over the top of the yogurt, and then sprinkle each with 1 tablespoon of the remaining brown sugar. Arrange the dishes on a baking sheet or in a large baking pan and place under a preheated broiler under the sugar starts to bubble and turn dark (1-2 minutes). Serve immediately.