Put all [B] ingredients into a bowl. Mash the bananas as you mix everything together (try using a fork or a whisk). You won't need to add sugar if using ripe bananas.
Add the [C] ingredients and mix some more. You could use one dairy product, or use a combination of milk and heavy cream. Just use whatever ingredient you have.
Now, add the [A] ingredient and mix lightly using a rubber spatula.
Pour into a pan and bake for approx. 20 minutes at 180℃ preheated oven. Test with a skewer. If it comes out clean, it's done.
Crusty on the outside, and fluffy in the inside. It stays nice and soft even after storing in the freezer (cover with plastic wrap and put it in a zip bag or a tupperware box).
Here's a variation with sweet potato (you could also use yam - in that case, make sure to add sugar) and flax seeds. It's really dense and moist.
Some other recipes from my "Easy with Pancake Mix" series - these are appraised as well Easy with Pancake Mix Crusty Cookies in 30 Minutes [Recipe ID: 2118393].
Story Behind this Recipe
Here's another recipe born out of my laziness. My 3rd recipe in my "Easy with Pancake Mix" series. I'm too lazy to even measure out the ingredients, so you only need a measuring cup and spoon to make these muffins. When you're a little hungry, you can make these muffins in 30 minutes and eat them freshly out of the oven.
You could also use kabocha squash or sweet potato paste instead of bananas. In that case, make sure to measure out 100g net weight. Please add sugar to your liking. Use 100ml vegetable oil to make your muffins even more dense. Chill in the fridge over night to make them even more moist.