Preheat the oven to Gas Mark 180`c. line 9 holes of a deep muffin tin with squares of nonstick baking parchment. Place the milk and butter in a large pan and heat gently. Stir in the spinach and bring just to the boil. Remove from heat and allow to cool for 10 minutes. Sift the gluten free flour and baking powder into a large bowl and add in the grated carrot, chilli flakes (if using) and season well with salt and pepper. Also mix in ¾ of the cheese and mixed seeds. Next, add the beaten egg to the spinach mixture, then add this to the bowl with the dry ingredients. Mix till just coming together (do not over mix as the muffins will become hard) Divide between 9 muffin holes, and sprinkle with the reserved grated cheese and seeds. Bake for 20-25 minutes, until risen and firm to the touch. Leave to cool for 5 minutes before serving either hot or cold.