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Heat 1 litre of buttermilk, whisk in 160 grams of sugar and 7 tablespoons of custard powder. You can substitute the custard powder with corn starch with some vanilla extract or vanilla sugar.
Slowly bring to a boil, you will visually see it thickening up. Stir in grated orange peel and season with more sugar to liking. Add in more sugar if you prefer the pudding to be sweeter.
Let cool off when the buttermilk pudding has thickened up nicely. To prevent a thin film from forming you can add a small sheet of greaseproof baking paper on top of the pudding.
This pudding can be served lukewarm or cold. Enjoy!