Spread bread slices out on a cutting board and leave out for a few hours to stale a bit.
Preheat oven to 350 degrees. In a small bowl, combine the sugar, cinnamon, nutmeg and salt, set aside.
Spread butter evenly over the six slices of bread (one side only—not both!), and cut the slices in to fourths.
Spray a round 8 or 9 inch baking dish with non-stick cooking spray. Arrange the cut bread slices around in the pan to make somewhat of a spiral pattern , keeping the buttered side up and the cut edges facing the same direction.
Sprinkle the raisins evenly over the top, followed by the cinnamon/sugar mixture.
Whisk the eggs and milk together in a bowl and pour over the bread. Allow to sit for 15 minutes so that the bread can absorb the liquid.
Bake for about 30 minutes, or until the top is golden brown. Serve warm. If desired, sprinkle some powdered sugar for garnish. In Ireland, they like to pour a bit of cream on top.