Add 2 1/2 cups boiling water to cover porridge oats in a bowl. Cream together butter and brown sugar.
Beat vanilla, eggs, buttermilk and the porridge oats mixture. Combine the dry ingredients and fold into wet mixture.
Fold in raisins. Divide batter into 4, for baking a dozen at a time. Let sit overnight.
Will last in the refrigerator for up to 6 weeks.
Batter freeze well for future baking. When thawing batter, do slowly in the fridge.
Bake as many as you want at 375F (190C) for 15-20 minutes.