Carina Jansson Nov 12, 2014:

I may be wrong, but as I understand it, "plankstek" is meat prepared on a peace of wood. But you can also prepare fish the same way, then it is "plankfisk".

SafeTex (asker) Nov 12, 2014:

@all Thanks everyone
A colleague has also told me that it is meant to refer to plankstek and I'm not sure what 'planked' food is (the alternative suggestion).
I already have food on a platter for 'matfat'

Norskpro Nov 12, 2014:

I am guessing that it means an evening when what's on the menu is "plankbiff", which is beef served on a wooden board. If you check "plankbiff" images on the internet you will see many examples.