Re: Molasses? In Mämmi?
Make your own "mämmi beer" at home by simply throwing some orange rind into a traditional kalja ... I put the orange into a hops bag during the ferment. I've used both dried Seville rind and fresh rind from oranges grown here. Kalja is usually chilled before it is fully fermented out to keep it sweet and low in alcohol, but I prefer to let it fully ferment for a dry brew.
Here's a recipe+method that's close enough as makes no nevermind to how I do it ... except I use from 50/50 to all malted rye, and mill it as I would for any other all-grain beer. You can ask at your local homebrew shop for help/advice on the correct amount for the batch size you are brewing. I've used LRE (the rye version of LME) and it works, kinda, but the entire point of this exercise is the grain.
Note: Some recipes for kalja recipes call for white sugar. Resist the option and use an appropriate amount of grain instead. Chances are the owner of the above mentioned homebrew shop will offer hands-on help with this one, just out of curiosity. If you're not a homebrewer, most such shops are more than happy to help neophyte brewers learn the ropes. Ask questions. Squeaky wheel & all that.
It's an interesting, very old-school brew, not for everyone's palate.