Preheat the oven to 400ºF/200ºC. Line a 12-hole muffin pan with paper cases.
Peel the kiwi and cut them into small dice chunks. To peel them, I cut the top and bottom off, then run a teaspoon under the fuzzy brown skin to loosen it, then slip out the green kiwi flesh.
In a medium bowl, beat the butter and sugar together until smooth, then beat in the eggs, one at a time. Beat in the milk and vanilla. Hint: it might 'split' slightly at this stage, but don't worry, it will come together with the dry ingredients.
Whisk the flour, baking powder, baking soda and salt in a large mixing bowl.
Add the wet ingredients to the dry mixture and gently mix to combine.
Gently fold in the diced kiwi.
Spoon into the muffin cases to ¾ full. Bake for 20-25 mins until the kiwi muffins are risen and golden. Allow to cool on a wire rack.