Cut the peeled sweet potatoes into cubes and prepare them. Put the boiled sweet potato water, butter, and sugar in a pot and simmer until the sugar and butter melt. Add the chopped sweet potatoes, mix them evenly, and cook about 70%. Cook until the outside is cooked and the inside is slightly crunchy, not fully cooked. When cooked thoroughly, it may be crushed in the process of mixing with the dough.

Boiled sweet potatoes that are soft and glossy are cooled naturally at room temperature. If you put the boiled sweet potatoes in the batter, the batter melts It's best to cool it down naturally at room temperature

Beat in room temperature soft butter, then add sugar 3 times and cream. First, mix the egg yolk one by one, and then add the egg whites three or more times. Add the sifted soft flour and baking powder and mix them as if drawing a # shape by standing a spatula. If you don't see any powder, add milk and mix. Likewise, stand the spatula and mix it as if you are splitting it. If you mix them together, the muffins become hard.

Add the boiled sweet potatoes and mix well with the dough. Put 70% of the dough in a muffin mold with parchment paper and bake it for 20-25 minutes in an oven preheated to 180. The baking time varies depending on the amount of dough and the specifications of the oven. Please take it out after testing the skewer. If you poke it with a toothpick and it doesn't come out, it's!!

Cool muffins well in a cooling net.