In a small saucepan, combine rolled oats, 1 cup of water, 1 tablespoon chia seeds, and 1 teaspoon vanilla extract over medium heat. Stir frequently for about 3-4 minutes until the oats are soft and creamy.

Once the oats are cooked, lower the heat and stir in 1 cup of full-fat coconut milk. Simmer for an additional 2-3 minutes, adjusting with more water if needed.

In a separate saucepan, heat 1/2 cup of coconut milk over medium heat. Create a smooth slurry with 1 tablespoon of cornstarch and a splash of water, then add it to the warm coconut milk along with 2 tablespoons of coconut sugar. Stir for about 2-3 minutes until thick.

To serve, spoon the creamy oatmeal into bowls and top with sliced mango and drizzle with the coconut sauce. Sprinkle with black sesame seeds or chili powder if desired.