Stir egg and sugar till super smooth (no electric mixer necessary but optional) for about 1-2 minutes. Then add oil and mashed bananas. Once combined, add all the dry ingredients to the wet dough and incorporate slowly until you no flour powder can't be seen. Scoop dough into muffin cup trays (use parchment muffin cups) or pour into baking loaf pan or on a baking tray for a try bake (add parchment paper on bottom for each option) and start baking. Follow baking times accordingly (see above) and use the toothpick proof-method to determine if your banana bread is ready. 

Remarks: I like to use only a hand whisk to stir the egg with the brown sugar especially in the morning; no noise while preparing the dough and everyone can sleep in. A hand mixer makes the egg more fluffy but does not really change the result of the consistence of the banana bread (muffin) once baked - either way you will receive a fluffy and moist banana bread. If you want to save time in the morning, the dry ingredients can be prepared the night before and mixed together already. 

Recommendations:
* Oil substitute: 60 ml coconut oil. Do not use extra virgin olive oil.  
**Gluten-free flour substitute: Bob Mills 1:1 gluten-free flour.