Preheat the oven to 350ºF. Add the room-temperature butter, cooking oil, granulated sugar, and brown sugar to a mixing bowl. Use a hand mixer or stand mixer to beat the ingredients together until they become light and creamy.
Mash the bananas well, then add them to the mixing bowl with the butter and sugar, along with the eggs, yogurt, and vanilla extract. Use the mixer again to beat the ingredients together until smooth.
In a separate mixing bowl, stir together the flour, baking powder, baking soda, salt, nutmeg, and cinnamon until well combined.
Pour the flour mixture into the bowl of wet ingredients and fold them together just until combined. Do not overmix.***
Divide the batter evenly between 12 greased or lined muffin wells.
Bake the banana muffins for 30-35 minutes in the preheated oven or until they have risen all the way in the center, have browned nicely, and a toothpick inserted into the center comes out clean (crumbs are okay, but no wet batter). Mine took about 32 minutes to bake.
Allow the muffins to cool for about 5 minutes, then carefully loosen the edges with a knife and transfer the muffins to a wire rack to finish cooling. Enjoy!
*Be sure to use room-temperature salted butter, yogurt, and eggs to ensure the batter comes together smoothly.**Plain Greek yogurt can also be used.***Avoid overmixing the batter by gently folding the dry ingredients into the wet ingredients. Mix until just barely combined with no traces of flour in the bowl. This will help create perfectly light and soft muffins!