Mix all the dry ingredients (bread flour, instant yeast, sugar, salt, and baking powder) in the bowl of the stand mixer.
Add the mashed sweet potato and 2 Tbsp of water to the dry ingredients
Start to knead the dough at a low setting (speed 2) for about a minute, until all the ingredients are mostly combined.
Add the olive oil next, and continue to knead for about 8 to 10 minutes, or until the dough pulls away from the bowl and forms a smooth, supple ball.
Note: Additional 1-2 Tablespoons of water (or additional bread flour) may be necessary depending on the protein content of the flour, the water content in the puree, as well as the humidity and temperature of the kitchen.
Remove the finished dough from the mixer bowl and place in a lightly greased bowl.
Cover and let rise until doubled, about 60-90 minutes***
When the dough is ready, punch down the dough then remove from bowl. Use a rolling pin to stretch and roll out the dough into a large rectangle, about 16 x 5 inch in size.
Starting from the long side, roll the dough tightly into a tight cylinder (like a sushi roll or cinnamon roll). Pinch the ends to seal.
Use a sharp serrated knife to divide the log into 16 equal pieces.
Place the buns on a parchment sheet or steamer paper, then cover and let rise for 20-30 minutes.
As the dough rests, boil water and prepare the steamer
Transfer the buns to the steaming pan and steam for 15 minutes, or until a toothpick inserted comes out clean.
Enjoy!
Note: You can store these steamed buns, well wrapped, at room temperature for up to 3 days. For longer storage, you can place them in a plastic freezer bag or airtight container and freeze up to 3 months, then defrost them at room temperature or steam them again for just 10 minutes to enjoy them just like fresh.