This is clearly a sinister scheme of some sort. So I'm obviously going to jump aboard and do my bit to edge the world towards destruction/domination/distopia!
The malt is crushed. According to Wiki, mämmi dates back to at least the 16th century, and may go back as far as the 12th (possibly even earlier).
I assume the lack of detail regarding temperature is due to primative or limited understanding of the process involved -- it is a recipe for cooks...
Mämmi is a Finnish pudding style thing which is basically rye malt and rye flour that's been mashed then baked (though commercial variants often cut corners and use molasses to sweeten it instead). It's traditionally an Easter dish, but is no less tasty for the rest of the year... though I admit...