Dissolve the yeast in the water. While the yeast sits a minute combine the flour and sugar in a separate bowl. Add in the yeast, oil, and salt. Knead for 3 minutes.
Let the dough rise for about an hour or until double in size.
While the dough is rising, make the filling. Drain the beans and boil until extremely soft, then drain out most of the water from the pot.
Mash the beans with a fork and add in the sugar and allow to reduce to on low heat stirring constantly. Taste the paste to make sure it’s to your liking- I prefer less sweet and a bit nutty so I add a teaspoon of tachina. You can add more sugar if you prefer a sweeter flavor.
Using an immersion blender or masher, blend to desired consistency. I prefer super smooth but others like the filling of their buns with a little texture
Let filling cool. Prepare a steamer basket or if you are like me and don’t have one, take a small aluminum tin and using a knife cut holes into the bottom of it. Place it on top of a pot of boiling water.
Take the dough and add in about 2-3 tbsps flour to make it less sticky.
Break the dough into 6-8 portions and flatten each portion into a circle with a thick middle and thinner edges.
Place a spoonful of the filling in the center of each circle and pinch closed on top.
Place in your steamer and cover letting the buns steam about 15-20 minutes. (My make shift steamer was a tinfoil pan with holes in the bottom. I covered it with a lid to a soup pot.)
Let cool and enjoy. They keep well overnight in the fridge if you can make yours last that long!