to make a chocolate 'collar' like the one below.

Have you seen this thread by ShirleyW on wrapping a cake in chocolate:

http://cakecentral.com/cake-decorating-ftopict-56654-.html

HTH

Thanks Jan. I'll have a look at that.

Also, is there any way to make the chocolate less prone to melting?

Candy Melts, chocolate chips and the barks (almond/chocolate confectionary coatings) are more stable than "real" chocolate.

There's modeling white chocolate (candy clay):

http://www.cakecentral.com/cake-decorating-ftopict-622286-.html

HTH

Wrapping a cake in chocolate isn't hard...it's just messy! When I made the cake in my avatar I swear there was chocolate everywhere...including the ceiling fan!
I used freezer paper to make mine....cut it to length, fold it into thirds, spread it with chocolate and off you go!


Jodie

I have no idea but I'd like to know too!

Okay....I'll try to do an explanation. I baked and iced my cakes and put them in the fridge. I melted white and semi sweet chocolate over simmering water then turned off the heat and left it on the pans to keep it warm.
I measured around the cakes with string so I'd know how long to make the freezer paper. I made the freezer paper about 2 inches longer than I needed it. I folded the paper lengthwise into thirds to make it stiffer and easier to work with.
Measure the height of the cake and mark the height on the freezer paper. That will let you know how high to make the chocolate. I made the back layer of chocolate taller than the cake, because I wanted a lip to hold in the fruit. I spread the chocolate on evenly, making irregular heights across the top. Carefully pick up the freezer paper after you let it sit 5 or 10 minutes or so and wrap around the cake. For the 12 inch tier I asked the DH to help me because it's was a long sheet. Tape the end of the paper and put the cake in the refrigerator. Once the chocolate is set, you can remove the paper, trim off any excess at the seam and get ready for the next layer. The next layer wasn't quite as tall as the first, maybe 1 1/2 inches shorter. The third layer, the most outside layer, was the shortest.
You just alternate chocolates. I used semi sweet, white, semi sweet. on the 12 inch Then on the middle 9 inch tier I did white, semi sweet, white. The top tier 6 inch tier was semi sweet, white, semi sweet. Just chill and remove the paper between layers! The cake was easy to stack, then just add fruit.
I hope that makes sense!

Jodie