Preheat the oven to 350 degrees F. In a bowl, whisk together the flour, baking soda, salt and spices. Set aside. Line a muffin tin with liners.
In a large bowl, whisk the egg and brown sugar together until smooth and no lumps remain. Add in vanilla extract, olive oil and bananas, whisking again until combined. Gradually add in dry ingredients, mixing until just incorporated. Stir in the milk and mix until just combined. Fill each muffin liner 2/3 of the way full with batter (I use a 1/4 cup measure to get the muffins to be of equal size). If you’d like, you can place a very thinly sliced banana slice on top of the muffin before baking.
Bake for 15-17 minutes, or until tops are no longer wet and become slightly golden. Remove and let cool until cool to the touch.