Preheat the oven to 180 degrees C. Line 12 muffin cups with paper liners or generously grease with cooking spray.
In a large bowl cream together the butter and sugar until light and fluffy. Beat in the eggs one at a time, mixing well after each one. Stir in the molasses. Combine the wholemeal flour, plain flour, cinnamon, ginger, bicarb soda and powdered milk; stir into the molasses mixture alternately with the water. Mix just until blended. Fold in raisins. Spoon the batter into the prepared muffin cups.
Bake for 20 to 25 minutes in the preheated oven, or until the top of the muffins spring back when lightly pressed. Cool for about 10 minutes in the pan before removing to cooling racks.