I’m thinking of experiment with a candy bar by making a peanut butter base, covering it in chocolate, and on top making letters out of frozen blueberries and covering those with chocolate too. I’m afraid that the berries will spoil though. Should I cook them first? Cook the whole thing? Any other alternative that I’m missing? I’m rather new to the culinary lifestyle; I’m hoping that the culinary geniuses at the Dope will come through! 
Yes, I would AT LEAST cook the blueberries, preferably with sugar. Reduce the mixture into a more concentrated form. Even still, I’d refrigerate the finished product.
How long should I cook the berries for?
Hmmm… Old caterer’s joke. “Until they’re done.” Ok, well, um, let’s say until the blueberries have reduced by approximately half in volume.
how long do you want it to keep for? what about dried blueberries?
Ah, dried blueberries… Sounds like a good idea!
Out of the fridge… probably about 9 hours. Otherwise, until they’re eaten.
If you are only trying to keep them for nine hours, I wouldn’t worry about them spoiling, even with fresh blueberries.
Not that I have any experience with what you are plotting.
I agree, 9 hours would most likely be no problem. Make sure that the blueberries are completely covered and ‘sealed’ in by the chocolate. Otherwise, you might have a problem with oozing berries.
In the Lac-St-Jean region, a huge blueberry production area, I’ve bought chocolate-covered fresh blueberries. The berries were fresh, but we were told to eat them pretty soon. They were still delicious the next day.
Good luck, it sounds yummy!
In my chocolate-dipping days at Godiva, we would make blueberry cups first thing in the morning, and they were fine at the end of the night. Just fresh berries, not even completely sealed by chocolate. We did keep them in a chilled case until they were sold, but there’s no problem with them sitting out as long as they’ve set up and don’t melt.
The OP states that ‘frozen blueberries’ will be used. That’s why I suggested having them completely sealed in chocolate. But I agree that one day’s time will not produce a spoiled product.