Oslo (Norway) restaurant/café recs?

Hey all!

My wife and I are waiting to board our flight to Norway to spend Christmas with her family in Sarpsborg. However, we'll be spending about 10 days there and spending out nights in a hotel in Oslo, so we'll def have time to ourselves without family obligations. If anyone (local or not) has recommendations for favorite restaurants or cafés, please share them here! Especially stuff on the cozy and cheap(er) end.