You must never leave a Norwegean meal in a private home without saying "Takk for maten" to whoever cooked it. Very important, honor to your grandmother!
I visited Fleicher's Hotel in Voss, Norway for a meal with my wife. At the end I remembered to say "Takk for Maten" to the young girl waiting table. She was thrilled that the English people did this. And, of course, I was thrilled because she was thrilled... it was all very nice. Thank you Duolingo.
Yes, in a restaurant too, apparently. It may be a little quaint, but very charming.