Start with generously buttering the pudding basin and add plum conserve to the bottom of the basin.
Put flour, baking powder, mixed spice, softened butter and sugar in a large bowl and mix together with the hand mixer. You can also use your standing mixer with paddle attachment if you prefer. Start adding eggs one at a time and mix until incorporated. Don't overmix.
Add pumpkin purée and mix until incorporated.
Pour the sponge batter onto the pudding basin on top of the plum conserve.
Cover the pudding basin with large piece of baking paper and aluminium foil and tie with a string to secure (see tips in the post above).
Place a steamer rack or overturned saucer on the bottom of the large soup/stock pot and place your pudding basin on top. Fill the pot with boiling water half way up the side of the basin and cover with tight fitting lid.
Steam for 2 hrs (initially on a medium heat which you turn down to low once water comes back to boil), topping up with some more boiling water along the way if necessary.
After two hours check with the skewer as you would regular cake (pierce your pudding through the baking paper and foil). If the skewer comes out wet, keep steaming for another 20-25 min but if it comes out clean, your pudding is ready!
When done, turn out onto a plate and serve immediately with lashings and lashings of custard or cream!