Add the rolled oats, full-fat coconut milk, and water to a small saucepan over medium heat. Stir to combine and bring to a gentle simmer.
Stir in sugar and salt. Reduce the heat to medium-low and cook, stirring frequently, for about 5 minutes or until the oats are thick and creamy. Be careful not to let the mixture boil. Remove from heat and mix in the vanilla extract.
In a small saucepan, heat the full-fat coconut milk, sugar, and salt over medium heat, stirring until the sugar dissolves. Do not boil. In a small bowl, whisk together cornstarch and water to form a slurry. Stir the slurry into the sauce and cook until the sauce thickens slightly. Remove from heat.
Divide the oatmeal between two bowls. Top with sliced mango, a generous drizzle of the coconut sauce, and a sprinkle of toasted sesame seeds. Serve immediately and enjoy!
