Grease a 1.2-litre pudding basin and scatter about a third of the raisins inside.
Place the suet, cornflour, sugar, remaining raisins, breadcrumbs and marmalade in a bowl and mix together.
In another bowl, mix the zest, eggs and a pinch of salt. Stir the egg mixture into the suet mixture and pour into the basin.
Put together two large rectangles of greaseproof paper and a piece of foil the same size.
Keeping the sheets on top of each other, fold them over in the middle so that you have a pleat in the centre.
Place on top of the pudding, folding it down at the sides, to make a cover and tie tightly round the top of the bowl with string.
Make a string handle so that you will be able to lift the pudding out of the saucepan easily.
Trim so there is 3-4cm of covering left below the string – if it touches the water the pudding will become soggy.
Set the pudding in a steamer or in a large pan of simmering water – the water should come a third of the way up the side of the pudding basin.
Cover and steam gently for 2 hours. Top up with boiling water if needed.
To make the sauce, put the marmalade, caster sugar and 2 tablespoons water into a saucepan and heat gently until combined. Remove from the heat and add the gin. The sauce will thicken as it cools and is best served warm or at room temperature.
When the pudding is cooked, run a knife around the edge and turn out onto a plate. Pour the sauce over the top and serve with crème fraîche – its sharpness will cut through the richness of the pudding.