For the steamed pudding, butter a 1.2litre/2 pint heatproof bowl then pour the golden syrup into the bottom. Add the apple and mix.
Mix the butter and sugar in a separate bowl until light and fluffy. Stir in the lemon zest and vanilla seeds. Beat in the eggs one at a time, beating well 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. Cut a large piece of baking paper and a matching piece of aluminium foil. Place the foil on top and fold a pleat down the middle to allow the paper to expand. Place over the pudding and 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.
Put the covered bowl on the saucer and pour water into the pan to reach two-thirds of the way up the bowl. Cover the pan with a lid and bring to a boil. Reduce the heat and simmer for 1-1½ hours.
For the plum and pear compôte, heat a large saucepan and add the butter and sugar. Add the plums, apples, cinnamon sticks, cloves and ginger and simmer for 8-10 minutes. Simmer the sauce, stirring gently until it thickens.
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 and serve along with the compôte and custard.