For the Pancake Batter: Combine all the dry ingredients in a mixing bowl.
Whisk the wet ingredients in a measuring cup. Make a well in the center of the dry ingredients and pour in the wet ingredients. Mix until the batter comes together without any lumps.
Cover and set the bowl in the refrigerator for at least 3 hours or overnight. I stowed some leftover batter for 2 days and made the pancakes on the 3rd day and they tasted pretty good.
For the Fillings: Coarsely grind/ chop/ pulse peanuts and sugar, set aside. Keep the chopped banana and nutella handy.
To make Apam Balik: Heat a non-stick crepe pan or small skillet on medium flame. Once hot, rub some butter or lightly spray some vegetable oil, then pour a ladle full of batter and swirl the pan around to evenly coat the surface. Let cook for 1~2 minutes and once the top surface dries out and bubbles start to form, sprinkle the fillings and some melted butter on top. If adding banana and Nutella then add them on one half of the pancake, but chopped peanuts can be sprinkled all over the pancake.
Continue cooking till the bottom is golden brown and crispy, this will take another 1~2 minutes depending on the size of the pan and the intensity of the flame. It might take a couple of trials to figure out the optimum heat level to make good Apam Balik.
Roll up or fold the pancake and serve immediately.