Melt butter and toast oats in a medium sauce pan until golden and fragrant, approximately 1-2 minutes.
Add hot water and chopped apples. Bring to a boil and let simmer for 20 minutes, stirring occasionally.
Stir in milk, vanilla, cinnamon, nutmeg, allspice and salt. Cook for another 10 minutes. Remove from heat and let sit for about 3 minutes.
Divide into 5 bowls, or prepare for freezing (see link in notes above). Add pure maple syrup or sweetener of choice to taste. Hint... taste before adding sweetener as you may decide you don't need it. Top with 1 tbsp of chopped walnuts and enjoy!