Preheat the oven 200°C /180°C fan /gas mark 6.
Grease a 25cm x 20cm ovenproof dish with butter.
Into a saucepan, mix the custard powder, 1 ½ tbsp caster sugar and 3 tbsp of the ProZero and mix to a smooth paste.
Stir in the vanilla bean paste and remaining ProZero.
Bring to a gentle simmer, stirring continuously until thickened. Set aside.
Spread the butter onto the bread slices, before cutting into triangles. Arrange the triangles in the greased dish, overlapping the slices, top with the sultanas.
Pour the custard over and stand for 5 minutes to allow the bread to absorb the custard.
Mix the spices with the remaining caster sugar and sprinkle over the top of the pudding.
Bake for 35 minutes, or until golden. Sprinkle with more sugar and serve warm with spray cream