Clean and peel the sweet potatoes, steam until they are cooked and leave to cool.
You can check they are cooked by sticking a fork in them. Mash finely, add the sugar and mix it in.
Mix the cassava flour and baking powder and mix into the potatoes.
Add the milk a little at a time and mix it in. You want the mixture to be a thick dough, add more or less milk to adjust the consistency. Leave for 1 hour.
Deep fry small balls of the dough in medium hot oil until cooked.