To make the sponge, simply mix together the shortening, flour, baking powder, currants and lemon zest in a mixing bowl. Pour in milk and mix well to create a soft dough, which should be sticky to the touch.

With your hands, rub butter onto the base and sides of a pudding basin before spooning the dough into it.

Fold a piece of greaseproof paper and cover the pudding basin and use string to tie over the ends. Place a damp cloth on top of the greaseproof paper, tying the ends of the cloth.

Fill a pan large enough to accommodate the pudding basin about half way with water. Place the pudding basin into the water and cover the pan with a lid or foil. Bring the water to a boil and simmer for an hour.

For the custard, whisk egg yolks and sugar in a small bowl until slightly frothy.

Bring milk and cream to a simmer in a small saucepan then pour the mixture onto the eggs, a little at a time. Whisk well with each addition. Once all combined, pour the mixture into the saucepan and cook on a low heat, using a spatula to stir until thickened. The custard can be served warm or cold, so place into the fridge to cool if you wish.

Once the sponge is done, slice into wedges and place onto a plate. Drizzle the sponge with custard and serve.