Put the soy milk in a small saucepan and heat a little over medium heat. Add the frozen berries, oatmeal and agave syrup and bring to the boil while stirring.
Add the cocoa as you like and stir the porridge vigorously again. Depending on the taste and the desired consistency, let the porridge simmer a little while stirring.
Pour the porridge into a bowl and add the banana slices.