Prepare the filling first. Mix all ingredients well in a bowl. You can taste it first if you wish. If it's not sweet enough, you can add in some more sugar.
Using a small teaspoon, scoop out balls of filling and shape into rounds. Set aside till all balls are completed, set them in the fridge or freezer.
For the dough, place glutinous rice flour in a bowl, remove about 1 tsp of flour and reserve for use later. Add in pumpkin powder and mix well. If you are using food coloring, you do not need to remove the 1 tsp of flour.
Add in water by 3 batches to mix with the flour. After adding in 2 batches of the water, slowly add in water bit by bit, if needed. Knead with your head so that you can have a better feel of the dough. It should not be sticky to your hands, and feel soft like your earlobe. If the dough becomes sticky due to too much water, knead in more flour until it doesn't stick.
Once the main dough is ready, remove a portion of it. Add in charcoal powder or dark cocoa powder or black coloring. Knead till color is even. If you add in powder, you might need to dab your fingers with some water to add to the dough so it does not get too dry.
For shaping, divide yellow dough roughly into 4 portions. Roll into balls.
Divide into 3 portions for each ball of dough - face + 2 ears. Flatten the face dough with your thumb, into a bowl-like dough. Place filling into the dough and seal the ends properly, so that the filling will not leak out during cooking later on. Roll the dough in between your palms lightly to smooth out lines, if any.
Do step (6) for all yellow dough. Set aside on lined plate or tray. Cover with cling wrap or damp towel.
Now to prepare the facial details, roll out small tiny balls of black for eyes + nose + eyebrow. You might need a sharp knife (cut) and toothpick (move the dough onto the yellow dough) to help you. You would need to work quickly as the black dough required is very small, and they tend to dry out and crumble easily. You can dab your fingers with some water if so.
Place the black details onto the yellow dough, cover with cling wrap until ready to cook.
Prepare water in a saucepan that is of enough height. Bring it to a boil on medium heat. Once boiling, lower heat to let the water come to slow simmer. Place tang yuan dough into the pot of water. I've used a ladle to help me - place the tang yuan onto the ladle, place into water, and gently shake it out of the ladle.
Cook the tang yuan until they float. Cook further for about 1 min more, to ensure that it is completely cooked. If you are not eating immediately, you can place them into a bowl of water first.
Serve with warm ginger tea/soup, red bean soup or simple syrup water.