this dish is traditional, some parts of country make it sweetened (flour and/or syrup) or regular (basically baked mashed potatoes)
i started by boiling 3 kg potatoes (floury work best, like with mashed potatoes). traditionalists say you should cook the potatoes with the skin on, but i figured it's easier to peel them raw than cooked and hot. besides, mom cooks them peeled...
after the potatoes were done, poured out the water and added 2 dl of all purpose flour and mixed well, put the lid on and left to "brew" overnight (if not overnight, then at least for several hours). ideally the pot should be then placed in a warm place. luckily the fireplace had been going on at the shack, so the mantel was quite warm, but you could set the oven for 70C and keep the pot in there.
next day i buttered (generously) four 1,5 liter foil pans. normally i would stay away from foil pans, but they make freezing so much easier
next, i added 1 liter of full fat milk, 2 tsbp of dark syrup (something traditionalist shy away), salt and liquid fat (butter and vegetable oil)
not pretty, but wait until this gets...
... mixed well. the mixture should be rather "runny", a lot more so than mashed potatoes
...and baked. blobs of butter on top and optional, but will definitely make a difference in taste
baked three casseroles for 3 hrs in 175C, froxe one for later use (who says this traditional christmas dish cannot be eaten, say, on easter!?)