1. Soak raisins in Irish Mist overnight. Drain off excess.
2. Preheat oven to 350. Generously butter an ovenproof dish. Using the remaining butter, butter both sides of bread slices & cut each into fourths.
3. Arrange a single layer of bread slices in the dish, slightly overlapping. Scatter with some raisins. Repeat with one more layer of bread then raisins. Press down gently.
4. Heat the cream & milk until just to a boil. Remove from heat. Meanwhile, whisk together the egg yolks & sugar in a heatproof bowl over simmering water until thickened. Remove from heat and beat in the cream mixture.
5. Pour two-thirds of the custard mixture over the bread and let stand for 30 minutes.
6. Pour remaining custard over soaked bread in dish and arrange the rest of the bread on top. Press down firmly so the custard comes halfway up the bread. Bake 30 to 35 minutes or until golden brown.