First off I am so excited that there is a cupcake forum!!!!! I just found it.
As you can tell by my name here, I do mostly cookies....but I LOVE cupcakes.

My question is how do you add fruit flavoring to buttercreams? Can I add some of those fruit filling sleeves that you get at cake decorating stores for filling your cakes? Is there any other way to get real fruit in them. I use a marshmallow buttercream for most of my cupcakes.

Any advice or recipes would be extremely appreciated!

I typically make either an American or a Swiss Meringue buttercream. If I want fruit flavor, I just add fruit puree

I'm fortunate because I can buy several kinds of frozen fruit puree from where I work, but you can easily make your own by cooking down the fruit with a little sugar (doesn't need much because of the sugar in the buttercream), then run through a food processor and sieve. You can use fresh fruit, although frozen fruit works great as well. It's also easy to make extra puree and freeze it for next time.

You probably could add some of the premade fruit fillings - just experiment a little

I mix store bought all fruit jam with buttercream and people love it.

I'm also mostly SMBC - but I just add home made fruit puree to it. I don't usually cook the fruit. Generally I buy frozen fruit, throw it in a bowl with some sugar and let it macerate. Then I push it through a mesh seive. I make big batches of the puree and keep it in the fridge to use as I need it. It also freezes well.

cookiemookie, could u share your marshmallow buttercreme recipe? TIA

Sure, it's not my recipe.

I got it on this site.

http://www.cakecentral.com/cake_recipe-2110-Marshmallow-Creme-Buttercream.html

It is delicious!

I did experiment with the fruit filling I had and it was fantastic! Everyone loved it. I added it by the spoonful till I liked the way it looked and tasted.

I just add enough jam until I get the right flavor.

thanks for the link