I'm not a big "blueberry syrup" fan, but my husband LOVES blueberry syrup on his pancakes, so I actually make this for him. This time around I canned them in 1/2 pint canning jars as we've found that the syrup only stays good in the fridge for about 3 months (and that's OUR fridge which is a nice one) before it starts to ferment, so the 1/2 pint canning jars saves us from syrup going to waste.
Now just to warn you "thick syrup" fans out there. The FDA does NOT approve the use of corn starch in canning recipes as it's not pure enough and lead to problems. They suggest using a product called "ClearJel". The cheapest place I've found this stuff is on Amazon.com (and yes that's even after shipping costs), so I'd suggest getting it there. It's not too terribly cheap, but if you want thick syrup I'd really prefer to adhere to the FDA standards for these things. I actually ordered some for myself recently to make home made pie fillings (a new area for me), and am looking forward to that :). So, anyway, if you are going to make thick syrup and don't want to pay for "ClearJel" I'd suggest just pouring out the amount of syrup you want to use into a pan before breakfast/dinner/whatever and add your cornstarch to the liquid, whisk to combine and then heat to boiling for a few minutes. That should definitely take care of any thickness issues.
And now onto the recipe!
Blueberry Syrup (based on Blueberry Pancake Syrup)
Canning Vessel and canning jars (and other canning implements as outlined in the Basic Materials Post)
1 Large pot to make the blueberry pulp in
1 Pot to catch the blueberry syrup in
1 cheesecloth lined colander or wire mesh sieve
4 Cups Blueberries rinsed and drained (I always use frozen when I do this, so that would be 2 lbs of frozen blueberries)
3 Cups Water (divided!)
3 Cups Sugar
Pour the Blueberries and 1 cup of water into a saucepan and let the blueberries defrost. Then take a potato masher and mush the crud out of them. Add about 1 tbs lemon juice to the mix to "wake up" your blueberry flavor and let simmer for 5 minutes.
Dump the entire mashy mess into a cheesecloth (or clean dishtowel you don't mind dying blue/purple) lined colander and let the juice drip for a bit (like seen above) into your catch pan (the colander should nest inside the pan you have for your catch pan to make your life easier and reduce wasting any juice). I also like to take the same potato masher you mashed your blueberries with to do some of the work for you here and I mash the blueberries down into the colander/cheesecloth and get as much of the juice out of the blueberries as I can that way. Once the mixture is cool enough to handle (stick your finger down into it and once you don't yank your finger out after 2 seconds going "OW" you're good to go), wrap up the blueberry pulp with the cheesecloth and squeeze the bejiggers out of it and squeeze the juice into your catch pan. Once your hands are purple, you feel like your hands are about to fall off and you can't really squeeze anymore juice out of your now purple cloth you are good to go. You should now have about 2 cups of juice in your catch pan. Discard the berry pulp that's left over.
Put the juice onto the stove and add the remaining water and sugar. Bring to a boil, making sure to stir to incorporate the sugar well. Once you are at a boil and you are sure the sugar is dissolved slap a lid onto your pan, turn down the heat to a simmer and simmer the entire mixture (with lid ON!) for 10 minutes. This will stop crystalization from happening while your syrup is thickening to...well...syrup like consistency.
Once the ten minutes are up, remove the lid, give it a stir and a taste and add lemon juice to the tartness you like.
Pour into canning jars leaving 1/2 inch of headspace using the methods outlined in the Ginger Syrup Post. Process in a boiling water bath for 30 minutes and you've got lovely blueberry deliciousness to be enjoyed through the cold winter months. I've found this recipe makes ABOUT 3 pints, but I've gotten as much as 4 out of it (depends on how juicy your blueberries are and how powerful you like your syrup).