Soak dried cranberries in 1/2 cup water overnight. Soak oats in 1 cup buttermilk overnight in the fridge.
Preheat oven to 375F (gas mark 5, 190C).
Stir brown sugar, oil, and eggs into the soaked buttermilk and oats mixture
Combine dry ingredients in a large bowl.
Add the wet ingredients to the dry, stirring until moistened and let stand while preparing the tin. We use a pop-over tin and this makes 6 muffins, but a regular muffin pan can be used if you adjust the cooking time. Lightly spray or oil the tin. Fill the cups to the brim. Bake for 20-25 minutes (or until browned and firm or they pass the toothpick test). Let cool slightly after removing from the tin.