In a dry frying pan placed over low heat, toast the walnut pieces until golden and fragrant, about 5 minutes, stirring occasionally. Transfer to a bowl and set aside.
In a small saucepan, combine oats, water or milk, cinnamon and sugar. Place over medium-high heat and allow to come to a boil, stirring regularly.
Once the oats have come to a boil, continue cooking over medium-high heat, stirring regularly, until the mixture thickens, 3-5 minutes.
Once the oats have thickened, divide over two serving bowls. Top with the yogurt, banana, toasted walnut pieces and chocolate. Serve immediately.
Recipe by The Tough Cookie at https://thetoughcookie.com/2016/08/19/chunky-monkey-oatmeal-brown-sugar/