Hello everyone - I am having hit and miss success with my cake fillings firming up.  I read somewhere - perhaps on CC, perhaps elsewhere (but didn't bookmark) a method using gelatine, i think, in the filling and pre-setting it in the relevant size cake pan.  Once it's set, remove it from the pan and place it on the layer.  Not sure of the details and would like to try it to test it's stability.  Is any one familiar with this?  I am a novice in the cake making and decorating realm but rapidly gaining ground with all the help from this forum.  My first post!  Thanks.

No, I've never heard of anything like that.  Personally, I don't think I'd really want fillings so firm that they "set up".

Many people just pipe a good dam of buttercream and put in whatever filling they like.

Now, if the filling is a butter based BC or a ganache, those can be put on, allowed to set in the fridge, etc.  I imagine that's how those picture perfect RBI cake layers are achieved.

That sounds kind of gross. I like my fillings to be sort of squishy, and soft. Like the icing. Maybenot has it right on, just pipe a dam. 

All you would have to do is dissolve some gelatin into your filling, spread it onto parchment so it's easy to remove, and let it set in the fridge, but you will end up with gummy bear filling.

Chewy in that sense in a cake doesn't sound good at all...