Place the sultanas in a bowl and cover with the Irish liqueur or whisky. Allow the sultanas to absorb the lovely flavour for about10-30 minutes before adding to the dish.
Next, generously butter an ovenproof dish. Butter each slices of bread on both sides and Arrange a layer, slightly overlapping in the base of the buttered dish.
Scatter over some soaked sultanas with the liquid and add another layer of bread slice on top and scatter over the remaining sultanas. Press down gently with a fish slice or spatula.
In a bowl whisk together the eggs, vanilla extract and caster sugar in a bowl until pale and fluffy.
Pour in the milk and combine until smooth. Pour over the bread mixture and leave to stand for about 30 minutes or until the bread has soaked up most of the egg mixture.
Preheat the oven to 160˚C.
Bake in the oven for 30-45 minutes in a bain-marie (a large roasting tray set up with water) until the custard is just set and the top is golden brown.
Serve the bread and butter pudding straight to the table with extra custard, whipped cream and or butterscotch sauce.