Peasoup is traditionally eaten every Thursday with pancakes. I remember from my childhood that we ate it in school and you could get it from a restaurant on Thursday, but nowadays I haven't seen it so often. It's specially traditionally now in shrovetide before fast. In Finland you eat peasoup with onion and mustard.

Rye bread is Finnish national food eaten every day by many. We don't especially like it, but thought bring it to you.

Karelian pies are from the Karelia area in Finland, but eaten in the whole country. There is rice porridge in rye crust. Pies are often eaten on breakfast or snacks.

The drink is traditionally made with white rhum agricole, lime, and cane sugar. 

It is served as an apéritif before starting a meal, both as a matter of tradition and because the drink itself is strongly alcoholic. 
A popular tradition is that of “chacun prépare sa propre mort” - each prepares his own death. Instead of serving the mixed drink, the host will simply put out the ingredients, and everyone will prepare the drink according to his or her own taste. Another explanation – if you pour a drink for your guest, how do you know his perfect portion? If you pour too little or too much you will not please your guest. 

Strangers to this custom probably ask where the Musik is. They most likely are told, Die Musik kommt später, i.e. the music "comes later". This is a euphemism for the latulence that the raw onions can provide uring digestion.