Wash potatoes thoroughly, and boil with the skins on in unsalted water. Peel the potatoes while they're warm, and blend them in a blender together with the butter.

After the mash has cooled a bit, put in half of the flour. Let it malt for an hour. Mix the rest of the flour. Let it malt in a warm place (not hotter than 120°F) at least 3-4 hours, or preferably overnight. Stir the mash a few times during malting.

Add enough milk to make a runny mash. Mix in the salt and the syrup.

Use a casserole dish big enough that the mix only fills it half way, as it will expand while cooking. Bake in 300°F for about 3 hours.