Preheat oven to 160C (325F) and grease muffin tin, or use muffin papers.
Process the walnuts in the food processor until ground finely but not until they become walnut butter, about 1-2 minutes tops. Remove from the food processor into the bowl you’ll be using for the dry ingredients.
Whisk together the coconut oil and honey until combined. Add both eggs and mix well. Add mashed bananas and passionfruit juice - stir in gently, and you can leave clumps of banana - it doesn’t need to be smooth. Stir in the vanilla.
In a separate bowl, stir the flour, almond meal, and walnut meal until just combined. Add the baking soda and salt and stir well, checking for lumps of baking soda. Add the dry ingredients to the wet, stirring carefully but not overmixing. Gently fold in the dark chocolate chunks.
Scoop evenly into muffin tin - you can fill nearly to the top of each muffin cup, as these do not rise very much. Sprinkle the top of each muffin with chopped chocolate and nuts.
Bake 26-28 minutes or until a toothpick inserted comes out clean. As ovens vary, the first time you make the recipe, check at 24 minutes.