Preheat the oven to 400 degrees F (205 Celsius). Place 12 muffin cases, or squares of parchment paper in a muffin tin. If you’re not using muffin cases simply grease the compartments of the muffin tin with sunflower oil, a little melted butter, or coconut oil.
Combine the flour, salt, cinnamon, mixed spice, baking powder and baking soda in a bowl.
In a separate bowl cream together the butter and sugar until pale, then add the egg.
Add the dry ingredients to the sugar butter mix, together with the teaspoon of vanilla, and the oatmeal porridge.
If the mix is a bit dry add in some of the milk. The amount of milk needed will depend on the consistency of the oatmeal porridge, but it should not be too sloppy – firmer is better.
Fold in the blueberries and white chocolate pieces gently as you don’t want to break the blueberries.
Spoon the mix into 12 muffin cases.
Pop into the pre-heated oven and bake for five minutes at 400 degrees F, then reduce heat to 350 degrees F (176 Celsius) and bake for around 15 - 20 minutes. They are done when a skewer or knife inserted comes out clean.
Leave to cool in the muffin pan for around 5 minutes before placing on a cooling rack.