Place the oats, water and milk in a large pan over medium heat and bring to a steady simmer for 5-6 min, stirring often to avoid the ingredients sticking to the pot. If it is too thick for your liking, stir in a little extra water or milk until desired consistency. Remove from heat.
Add grated apple, maple syrup, walnuts, apple cake spice and vanilla extract into the porridge and return to a medium heat for 1 min, until it returns to a simmer.
Divide across 4 bowls, top with a drizzle of syrup and sprinkle with Apple Cake Spice and some extra chopped walnuts.
To make a vegan and dairy-free version, use your favourite dairy-free milk.