For our Sing-A-Long Sound of Music brunch, I made twice-baked almond croissants, as published in a recent issue of Gourmet magazine. Although the original featured article showed how to make croissants from scratch (who's got the time?!), the article also suggests making these from store bought croissants.
You can make the almond filling and syrup ahead of time and assemble the croissants just before your guests arrive. I found that I used only half the syrup and could have used more filling (I used very large croissants, though).
The almond filled croissants turned out great...they smelled wonderful while baking, the almond cream was flavourful and the sliced almonds sprinkled on top were a nice toasty garnish. I didn't toast the sliced almonds before using and they ended up toasting well during the baking process.
So if you want to boost some old store bought croissants, this is a superb recipe to try!