Use a regular 12-cup muffin pan. Grease muffin pan or use muffin cup liners to line the muffin pan. No need to grease the pan if you use muffin cup liners.
Preheat oven to 350 Fahrenheit.
In a medium bowl, using electric mixer, beat 4 tablespoons of butter and 1 cup of white sugar on high speed for 1 minute until well-combined. You will get coarse looking mixture (not creamy).
Add 2 eggs to the butter-sugar mixture and continue beating for another minute until very creamy and very smooth.
Add mashed bananas, Greek yogurt, pumpkin puree, and vanilla extract to the butter-sugar-eggs mixture, and continue beating, using electric mixer, until well combined – for about another minute.
In a separate medium bowl, combine sifted flour (do not overpack the flour, when measuring it using measuring cups!), baking powder, baking soda and cinnamon. Mix until well combined.
Add dry ingredients into wet ingredients, and mix, using large spoon, just until combined. DO NOT OVERMIX. If there are lumps – they will work themselves out during baking. Fold in chocolate chips.
Fill muffin cups ¾ full. Bake for about 25 minutes. Cool on a rack for a little bit, then remove muffins from the pan and let them cool some more.