Preheat oven to 400 degrees F/ 200 degrees C. Pinch the sweet potato with a fork in several places and wrap it with aluminium foil. Bake for about 40 minutes or until soft when touched with a fork.
Let the sweet potato cool and then peel it and puree it in a food processor.
In a bowl combine sugar, yeast and some of the water. Mix and set aside for 10 minutes.
In a large bowl combine the sweet potato puree with the yeast mixture, salt and about 2/3 of the flour. Mix very well. Gradually add the rest of the water. Mix with a wooden spoon or with a hand. Make a soft dough that would stick to your hands. Add more flour if necessary but you need to leave some for the end, to coat the rolls.
Dust the dough with flour and leave it in the bowl, covered with film or parchment paper. Wrap the bowl with tea towels and leave it in a warm place for about an hour. It should double its volume.
Dust your hands with flour and make 5-6 balls out of the dough. Arrange them on a large baking tin, covered with parchment paper. Cover them and let them stay for another 30 minutes, to increase again their size.
Heat a large skillet or a non-stick pan. It should be at medium heat as if it is too hot, the breads may burn.
Bake the breads on the pan, flattening them with a wooden spatula. Cook for about 3-4 minutes on each side. Use kitchen tongs to hold the breads and cook them also on the sides.
When they are still hot, slice them horizontally with a sharp knife and spread the garlic butter on top. Serve immediately.