1 vanilla pod, split in half lengthways and seeds scraped out
For the sponge, butter a 1.2litre/2 pint heatproof bowl then pour the golden syrup into the bottom of the bowl.
Place the butter and sugar into a separate bowl and whisk until light and fluffy. Stir in the lemon zest and vanilla seeds. Add the eggs one at a time, beating between each addition. Fold in the flour and baking powder and mix to form a smooth, thick batter.
Spoon the sponge mixture into the buttered bowl. Take a large piece of greaseproof paper, then a piece of tin foil on top. Fold a pleat down the middle to allow it to expand when cooking and place over the pudding. Secure around the edge using cooks’ string. Fold a large piece of aluminium foil into a long strip and place under the pudding bowl to use as a handle later.
Place a saucer or small plate upside down into the bottom of a large saucepan. Place the foil covered bowl onto the saucer and pour water into the pan to two-thirds of the way up the bowl.
Cover with a lid and bring to a boil. Reduce the heat and simmer for 1-1½ hours.
For the custard, place the egg yolks and sugar in a bowl and whisk until well blended.
Put the milk, cream, vanilla pod and seeds into a saucepan and bring to the boil. Simmer for a minute, then pour onto the egg mixture and whisk in.
Return to the saucepan and heat slowly, or until the custard has thickened enough to coat the back of the spoon. Strain through a sieve into a clean pan.
To serve, remove the pudding from the saucepan using the foil strip to help you. Discard the foil and baking parchment.
Place a plate on top of the pudding and turn over, tipping out the pudding onto the plate. Cut the pudding into slices, place on plates and pour the custard alongside.