Does anyone have any tips for keeping the grease in buttercream frosting from seeping into my royal icing "accessories"? I know I could add them at the last minute, but that's sometimes not possible and can present its own problems.

The only thing I can think of is to put a small piece of wax or parchment paper under each piece. It's just the nature of the beast. Grease breaks down royal and there isn't anything you can do about it.

I actually didn't realize you could use BC with RI. I mean, maybe to place a couple of RI flowers on a cake but any more then that, I always thought wasn't possible. I'm sorry I'm no help at all!

Mini marshmellows
<... I actually didn't realize you could use BC with RI. I mean, maybe to place a couple of RI flowers on a cake but any more then that, I always thought wasn't possible...>

This is a myth I have been trying for years to dispell
Once RI has completely dried there is little problems w/placing them on b'cream. The thicker the 'base' of the RI item the better. ie: roses do much better than apple blossoms etc.

For plaques use mini marshmallows if you must. I have place many, many items directly on my b'cream cakes w/o problems - no melting of the RI; no grease problems. But yes, small thin flowers or lettering can absorb some grease and look stained. Don't count on standing items up by pushing them into the icing &/or cake....most of the problem here is the *moisture* in the cake but it will soften and break. Instead attach a sucker stick to them to be inserted into the cake.

mini marshmallows!?! I NEVER would have thought of that! I like your idea too of just building up the base where possible. Why didn't I think of that???

I agree, it's depends greatly on the thickness of the item you are placing on the cake. Make sure that your RI decor is completely dry before you place it on the cake. I just made this cake for Easter with RI lilies. I made a mound of buttercream before placing the flowers. The flowers were on the cake at least 12hrs. before serving, and they held up just fine.

oh that's lovely! so the flowers have some hidden thickness? because they look quite thin and dainty.