I found this mold today when I was puttering around at one of my favorite cake decorating stores (Sugar 'n Spice in Daly City):
It's the Sea Shell Flexible Mold by LorAnn. It doesn't say anywhere on the packaging what it's made of, but I'm guessing silicone. It has a yummy recipe on the packaging for Cream Cheese Mints, which I tried as soon as I got it home. All the recipe calls for (other than the mold) is 3 oz. room temperature cream cheese, 2 1/2 cups of powdered sugar (I wound up using closer to 3 1/2 cups), 1/2 cup of granulated sugar, paste or gel food coloring, and a few drops of LorAnn Spearmint oil. You'll also need a cookie sheet with a piece of waxed paper taped to it.
Start by sifting the powdered sugar and weighing out the cream cheese.
Combine them together, and add the food coloring and spearmint oil to taste (start with about 4 drops of each; you can always add more of either).
The mixture should be the consistency of pie dough. You might be able to tell it was still rather creamy here, and it needed to be stiff enough to be kneaded.
I sifted in another cup or so of powdered sugar, and it became kneadable.
Put the granulated sugar in a dish, pinch off small balls of the cream cheese mixture, and roll them in the sugar. The granulated sugar will keep the mixture from sticking to the mold, so don't use it sparingly.
Press the balls into the recesses in the mold, and wipe away any excess. I figured out after this first round of four that I was rolling the balls a little too big; easily fixed.
Invert the mold, and give it a hearty smack onto the waxed paper or your hand to release the shells.
Chill them in the refrigerator until ready to serve. When you're finished, wash the mold in warm, soapy water, rinse it well, and allow it to dry flat. You can also use the mold for molding butter; just press the butter into the mold, chill the mold, then unmold the butter when it's firm. I'm definitely saving that trick for my next dinner party!