Bake the sweet potatoes, either in the oven for about 30-40 minutes or in the microwave for 8-10 minutes (timings depend on size of sweet potatoes). Once cooked until soft, scoop out the flesh and mash until smooth.
Combine the sweet potatoes with the other ingredients and enough warm water to make a very soft, wet dough. Using one hand, bring all the ingredients together and mix thoroughly for 5-10 minutes or until dough becomes elastic.
Cover dough loosely with cling film and leave in a warm place for 30 minutes.
Divide the mixture into 4 equal portions. Oil your hands, so they don't stick to the dough, shape into flattened rounds and set aside to prove for another 30 minutes, covered with a damp towel.
Melt a little butter in a small, high sided pan (or whatever kind of pan you have) and cook each round over a low heat for 8-10 minutes on each side until browned and cooked through.
Repeat process with remaining bread, keeping the cooked Bola soft by covering with a clean tea towel on a cooling rack.