Place peeled and seeded mandarin oranges into a Nutribullet or food processor and pulverise until you get a smooth juice. Strain through a fine sieve, using a tablespoon to press on the mandarin oranges pulp to release more juice. Add the mandarin orange zest to the juice and set aside. You need 250ml of mandarin orange juice.
For the Red Bean Paste filling:
Pour the soaked overnight red beans and water into a medium pot. Add a further 2 cups (250ml) water and bring to a rolling boil. Turn the heat to low and simmer for 1 hour or until red beans are very soft. Stirring occasionally.
Then add the mandarin orange zest, extra virgin olive oil and agave syrup into the pot together with the corn starch mixture. The paste will thicken almost immediately once the corn starch mixture is added. Stirring frequently to avoid sticking and burning at the bottom. Cook on low heat for around 5 minutes.
Turn off the heat and remove the pot from the hot stove and lightly mash the red bean paste with a potato masher. Then let the red bean paste cool down. Chill in the refrigerator until ready to use. The paste will thicken further as it cools.
For preparing the dough:
Warm the rice milk in a small pot for around 2 minutes, then turn off the heat. Add in the rest of the wet ingredients, combine and mix well.
In an electric mixer mixing bowl, add in all the dry ingredients.
Attach the mixing bowl to an electric mixer and then attach the dough hook. Using low speed, mix the dough for about 30 seconds or until ingredients are well combined.
Continue on low speed and gradually pour the warm rice milk mixture into the well in the large bowl for about 2 minutes.
Then slowly add in the mandarin orange juice with mandarin orange zest added prepared in step 1 and continue to mix on low setting for another 2 minutes.
Stop mixing and then use a rubber spatula to scrape the sides and bottom of the mixing bowl.
Mix on medium setting for another 5 minutes or until dough is well combined.
For stuffing the dough:
Lightly grease all the muffin cups with some vegan butter.
Scoop and place small amount of wet dough into the bottom of each cup of the muffin pan (about 1cm thick).
Then add 1½ tablespoons of red bean paste into the centre of each muffin cup, gently flatten the paste slightly.
Fill each muffin cup with the rest of wet dough until nearly the edge.
Let the dough rise for about 20 minutes.
For cooking the bun:
Preheat fan-forced oven to 190C or 375F. Bake the buns for 15 minutes or until lightly golden.
Remove and place the cooked buns on a cooling rack.
Reheat by covering the buns with aluminum paper and bake in the oven for 5 minutes or in microwave for 45 seconds or until buns are soft.