Very similar to the Ashkenazi Jewish dish kugel, from which it is almost certainly derived, it is also typically made from potato. It is important that you use particularly starchy ones here – if you can’t find any, then add some cornflour (cornstarch) to the mix as it’s important that everything binds together well.
The perfect potato pudding is soft and fluffy, though many home cooks hold their own opinion on whether you should strain off the liquid when grating the potatoes, which gives a drier result, or keep the liquid, resulting in a moister dish. Both are good, it is simply a matter of taste. Commonly served with apple or lingonberry preserves, this also tastes delicious reheated.