Set your oven to 350°F (175°C). Line your muffin tin with paper liners.
This prevents sticking and makes cleanup easier.
Peel your ripe bananas completely. Mash them well with a fork.
You want a smooth consistency with few lumps.
Add melted butter to the mashed bananas. Stir in sugar, beaten egg, and vanilla.
Mix everything together until well combined.
Sprinkle baking soda over the banana mixture. Add a pinch of salt too.
Stir these ingredients in thoroughly.
Add flour to your wet mixture gradually. Gently fold it in with a spatula.
Don't overmix or muffins will be tough. Mix just until flour disappears completely.
Fold in chocolate chips or walnuts now. This step is totally optional though.
The muffins taste great either way.
Scoop batter into prepared muffin cups. Fill each cup about two-thirds full.
This allows room for them to rise.
Place tin in preheated oven carefully. Bake for 18-20 minutes exactly.
They're done when golden brown on top. A toothpick inserted should come out clean.
Remove muffins from oven immediately. Let them cool for 5 minutes.
Transfer to a cooling rack afterward.