Preheat the oven 180c fan. Prepare your muffin tins.
Begin by adding the self rising flour, oats, sugar, cinnamon and baking powder to a large bowl, mix well.
For the wet ingredients: add the melted butter, milk and eggs to a jug, whisk well.
Add the grated apple, mashed banana and grated carrot to the bowl with the flour, mix with a fork.
Pour the wet ingredients in and stir to combine. Scoop into the muffin tins.
Bake in the oven for 20-25 minutes until golden on top and cooked through. Test with a cocktail stick- when it comes out clean they're done.
