Heat the oven to 180C and line a muffin tin with cases. Mix 100g muesli mix with flour, baking powder and sugar. In a separate bowl, combine milk, vanilla, apple, olive oil and 2 tbsp nut butter. Stir it into a dry mixture and combine together.
Divide the mixture between muffin cases, then mix together the remaining muesli with nut butter, demerara sugar and pecans. Spoon this mixture over muffins.
Bake for about 25 minutes, until muffins have risen and are golden.