Hi! I have a cake this upcoming week and she asked for a blueberry filling for between the layers. What is the best one to buy or is there a good recipe out there? Thanks!

Harry and David's is the absolute best to use as a filling unless you make your own. I making your own.  

Take blueberries and add a small amount of water, don;t add a bunch to drown them.  Bring to a boil and let simmer until the berries burst and break down, add a slurry of cornstarch and water to thicken the sauce.  Be sure the berries are at a brisk boil in order for the cornstarch to thicken correctly.  Voila, blueberry filling.  Let it cool and use as you would any other filling.  If it is a little too tart then add a small amount of sugar and while you are cooking it put 1tsp of lemon juice to bring out the flavor of the berries. 

I made this cake The other day, the filling was to die for. http://leitesculinaria.com/3041/recipes-marbled-lemon-blueberry-butter-cake.html

thank you its perfect!