Peel the sweet potatoes. Soak in water, then boil until soft.
When boiled, drain, and mash while hot. Mash well. You may also want to pass them through a strainer for a smooth texture.
Mix in the condensed milk. Add more if you have a sweet tooth.
Add the egg yolk and mix. If the batter seems too firm, add milk to soften it up a bit.
Chop one corner off of a plastic freezer bag, and then seal the hole you just made using a clip. You may want to use a spoon to scoop the batter into the bag!
When you've poured all the batter into the bag, remove the clip and squeeze into the cupcake liners.
Top with cinnamon and bake in a 170℃ oven for 15 minutes.
Story Behind this Recipe
I wanted to make sweet potato bites, but I was short of heavy cream! That's when I was inspired to make them with condensed milk instead of heavy cream and sugar.
Using a piping bag makes things easier when transferring the batter into the cupcake liners. Make sure the bag is strong enough, because it will tear if the batter is firm! The firmness will depend on the kind of sweet potatoes you use, but you should try to make a batter that is only slightly firmer than custard cream.