Combine all the wet ingredients together in a large bowl, eggs, yogurt, maple syrup, butter, vanilla extract, and banana and mix thoroughly.
Add in the dry ingredients (oats, whole wheat flour, chocolate chunks, chia seeds, baking powder, cinnamon, and salt and fold gently so that the batter is not overmixed.
Spray two silicone molds with cooking spray.
Use an ice cream scoop for ease and fill the molds to the top.
Pour 1 cup of water into the Instant Pot and place the wire rack down to stack the first silicone mold on top. (Note do not put the lids on the molds - they might melt!)
Place 3 metal mason jar tops on top of the first silicone mold to allow for the muffins to expand.
Place the second mold on top of the mason jars.
Put on Instant Pot lid and turn the pressure release knob to the sealed position.
Cook on high pressure for 10 minutes and then use the natural release for 10 minutes to release the extra pressure.
Let the muffins cool and serve with a little bit of butter or your favorite nut butter!