Preheat oven to 190 degrees celsius (fan-forced). Line a 12-hole muffin tin with muffin cases.
Mash the banana in a bowl.
Add the greek yoghurt, honey, vanilla extract, melted coconut oil and egg and whisk until well combined.
In a separate bowl, sift the plain flour, bi-carb soda, cocoa powder and salt. Stir to combine.
Make a well in the centre of the dry ingredients and pour in the wet mixture.
Very gently fold the mixture with a spatula until just combined (don't over-mix the ingredients).
Fold through 1/4 cup of the chocolate chunks.
Divide the mixture equally between the muffin cases (filling to 2/3 of the way).
Sprinkle the remaining chocolate chunks over the top.
Bake for 15 minutes or until cooked through.
Allow to cool in the tin for 5 minutes before transferring to a wire rack to cool completely.