Butter the inside of two 1.2 litre pudding basins.
Spoon 100g of jam into the base of the basins.
Beat the butter, golden syrup, and sugar until light and fluffy.
Mix in the eggs and flour gradually until a dropping consistency is reached.
Add a splash of milk if the batter is too thick.
Spoon the mixture into the basins until three quarters full and smooth the surface.
Cover loosely with cling film and microwave for five minutes.
Check that a skewer inserted into the centre comes out clean.
Let the pudding stand for five minutes before inverting onto a plate.
Top with extra jam and serve with custard.