Vastelaven is something I heard not so long ago from my workmates at work. It has to do with the time before 'vasting' before easter. It's the time that Christians of certain churches have a great meal right before they will stop eating and keep it to certain amounts of food and drinks to pay respect to some event in the religion.
Vastelaven is also the name of a certain bread with vanillecreme in it, a specialty that is bought by many in the same vastelaven time. I would say it has not much to do with the religious day, because as far as I know it has to do with a time of reflection and not about eating yourself full with all types of sweets.

I wondered about this weird, apparantly Norwegian, word 'vastelaven' so I went on the internet looking for it. I came out on a Dutch website with rhimes and old time songs, where this word vastelaven was part of(!). Vastelaven seems to have been coming from Germanic, and has therefore been used in both Dutch and Norwegian language. The Dutch variants became Vasteavond, vastelavend, it all comes down to the same meaning: vasten avond, the evening before the period of none or less eating and reflection.
Now I won't discuss whether the event itself is good or not, I prefer to stay outside religious and political discussion on my blogs, but at least I figured out that the weird Norwegian word, isn't really an original Norwegian word, as it's coming from the Germanic language of the old days.
Otherwise do I think that every country and every shop or bakery has their own 'vastelaven' specialties to sell and offer something special for that specific religious day and every region in a country or every country has a different specialty.
At Vastelaven itself we were visiting Laura and Hallvard in Brokke and made some vastelaven of our own with bread from the shop and some cream of a package. Delicious!

Some resources:
[NL: Baker en Kinderrijmen - Feestrijmen - Vasten Avond]
[Nordic Language History on Vastelaven]