Grease a 1 litre (1¾ pint) pudding basin and line the inside with a circle of greaseproof paper. Spoon the 75 ml (3 fl oz) golden syrup into the basin.
Mix together the flour, suet and sugar in a bowl. Stir in the egg and milk until thoroughly combined. Spoon the mixture into the basin and level the top.
Cover the basin with a double layer of baking parchment, securing around the rim with kitchen string. Cover with foil, scrunching it over the paper tightly to seal. Sit the pudding basin in the bowl of the halogen oven and pour in enough boiling water to come a third of the way up the side of the basin.
Set the temperature to 250°C (482°F) and steam the pudding for 1½–1¾ hours until the top of the pudding feels just firm to the touch and a knife inserted into the centre comes out clean. Leave in the basin for 5 minutes, then invert on to a serving plate and peel away the lining paper. Serve with warm vanilla custard (see