Make Muffin Mix: Take out a mixing bowl. And thoroughly mix flour, sugar, baking powder and salt together. Set aside.
Take out another small bowl. Slice off a piece of butter. Melt in microwave for 1 minute.
Crack 3 eggs into a separate large bowl. Whisk eggs well. Pour half of the melted butter in. Mix into the eggs.
Take out a strainer and place over the egg mixture. Pour flour into the strainer. Gently tap on the strainer and sift the flour into the egg mixture.
Finally, pour milk into the mixture.
Thoroughly mix and blend all of the ingredients together. The batter should be slightly runny and goopy.
Take out your rice cooker bowl. Brush the remaining melted butter into the bowl. Make sure to coat the sides so the cake don't stick.
Pour batter into rice cooker bowl. Place bowl into rice cooker. Set it to steam (찜) mode and let it cook for 40 minutes.
Once 40 minutes is up, use a toothpick and poke the middle to see if the cake has cooked all the way through. If is slightly wet, just let it sit in the cooker for 5-10 more minutes.
Enjoy with a cup of milk!