You will enjoy these soft and fluffy Malay-style sweet potato doughnuts coated in crystallized sugar. The doughnuts are easy to put together and don't use any yeast. The doughnuts can be fried, baked, or air-fried.
Cut the sweet potatoes into cubes and then steam on medium-high heat for 5 minutes. Mash while they are still warm and then set aside to cool down
Combine the cake flour, rice flour, salt, baking powder (if using), and cinnamon powder
Sift this over to the sweet potatoes and then knead into a dough. If you find that the dough is too dry, you may add a bit of water, teaspoon by teaspoon. If the dough is too wet (some sweet potatoes contain more moisture), then add a bit more all-purpose flour, one tablespoon at a time until you can get a soft dough that just slightly sticky to touch
Shaping:
Divide the dough into 12 equal pieces. Oil your palms with some oil or spray with some cooking spray. Roll them into a ball and then slightly flatten into a disc and then use your index finger to poke a hole into the middle to make them look like donuts with holes.
Deep-frying:
Preheat oil in a heavy-bottom pot over medium-high heat. When you dip a skewer in there, you'll see bubbles around it. Lower the heat to medium and add the donuts into the oil, 3-4 at a time. Gently flip them over as they cook to prevent the donuts from getting burn. The donuts will float to the top when they are cooked through. Remove to an absorbent paper towel and continue frying the rest
Baking:
Line a baking sheet with a parchment paper. Spray some cooking spray on the donuts or brush with oil. Preheat the oven at 350 F (180 C) and bake for 15 minutes at middle rack and then turn over and bake for another 10 minutes or until the inside cooked through
Air-frying:
Spray the basket with some cooking spray or brush with oil. Brush some oil on the surface of the donuts or use a cooking spray. Arrange the donuts in a single layer inside the basket of the air fryer and air fry at 350 F (180 C) for about 3-4 minutes. Flip over to the other side and cook for another 3-4 minutes or until the donuts are cooked through. The time is just a reference, you may have to experiment with the timing on your air fryer
The air fryer and baked version won't have nice even golden brown like the deep-fried version, just so you know
Prepare the crystallized sugar coating:
Put water and sugar in a large pan and bring to a boil over low heat, once it starts bubbling, add the cooked donuts and keep stirring and you will start seeing the sugar turns "whitish" in color because the sugar starts to form crystals. It may appear a bit wet at first, but it will dry up and turn even whiter after it cools down completely