Melted butter, for greasing
¾ cup treacle
Extra 100g unsalted butter, chopped, softened
½ cup brown sugar
225g self-raising flour
²⁄³ cup milk
½ cup currants
¼ cup golden syrup
Vanilla bean custard, to serve
Grease a 1.2L pudding basin with butter. Pour ½ cup of the treacle into basin. Put extra butter and sugar in a large bowl. Beat on medium speed for 4 minutes, using an electric mixer with paddle attachment, or until light and creamy. Beat in eggs, then fold in flour and milk and gently beat until smooth. Finely grate zest of the oranges, reserving the flesh, and add zest to batter. Add currants and stir to combine.
Spoon batter into basin. Cover with 1 sheet baking paper and 1 sheet foil. Secure tightly with kitchen string.
Put basin on a trivet in a large saucepan. Fill pan with boiling water until it comes ¾ of the way up the sides of basin. Bring water to a simmer over a low heat and cook for 1½ hours or until pudding is firm, topping up the water as necessary.
Meanwhile, use a small sharp knife to remove orange skin and pith. Cut into segments. Put golden syrup and remaining treacle in a small bowl and combine.
Remove basin from pan. Remove paper and foil and invert pudding onto a serving plate. Pour over syrup and arrange orange segments on top. Serve with custard.