To a big jug, add Butter (100 gram), Milk (1 cup), Vanilla Extract (1 teaspoon) and Egg (1). Beat them together. Mash Banana (2) in a bowl. Put them into the liquid and stir together.
In a bowl, prepare the dry ingredients: Self-Rising Flour (2 cup), Caster Sugar (1/2 cup) and Salt (1 pinch). Stir them together, and pour in the wet ingredients. Stir until they combine.
Use butter to grease the holes in the muffin pan. Put a quarter cup of the mixture into each hole. Put the tray into the oven preheated to 225 degrees C (440 degrees F) for 12 minutes. When done, let them cool for a few minutes, and serve.