For the custard, pour the cream into a saucepan, add the vanilla pod, seeds and cinnamon and heat until gently simmering. Remove from the heat, remove the vanilla pod and discard.
Place the egg yolks and icing sugar into a large bowl and whisk together.
Pour the egg yolk mixture into the cream, whisking well. Return the pan to the heat and cook gently, stirring until the custard has thickened slightly.
Grease a small microwaveable dish and place the sliced croissants into the bottom of the dish.
Pour the custard over the croissants. Transfer the dish to the microwave and cook on high for 2½ minutes.
Place the redcurrant jelly into a small saucepan and heat gently until melted.
To serve, remove the bread and butter pudding from the microwave, brush with the warm redcurrant jelly and dust with icing sugar.
