This project was originally published on my blog and my wife's blog. It was also posted on Make:Projects.
Halloween has always been my favorite holiday, but when it comes to dessert, my tastes have matured towards the gourmet. I wanted to create a Halloween treat for adults. Something not to be gobbled, but savored. As a kid, I thought shelled walnuts looked like tiny little brains. This gave me an idea: What if I coated them with candy for Halloween? I envisioned eating handfuls of tiny candy brains…laughing maniacally. That could be fun, but if they were placed in miniature edible skulls, it would really put them over the top. If those skulls were white chocolate… Well, now we’re talking!
I just needed a way to make the skulls. Sculpting each one with modeling chocolate would quickly become tedious, so making some sort of mold seemed like the obvious solution. Besides, modeling chocolate isn’t exactly the best tasting stuff on the planet. Perhaps it would be worthwhile to make them into some sort of crazy truffle. A white chocolate shell with a surprise bittersweet center sounded tasty.
The trouble with skulls is they’re quite complex with lots of nooks and crannies and undercuts. To do a somewhat realistic version would normally require sophisticated (i.e. expensive) multi-part molds. Luckily, I recently learned there are several companies that sell food grade silicone mold materials. The extreme elasticity of silicone made it the perfect choice for this project. I could use a one part mold and still get all the detail I wanted.
I ordered the silicone from MakeYourOwnMolds.com I Plan to try the silicone Plastique in the future, an easy to use 2 part putty, when I have a less ambitious shape to mold. This time, I got the CopyFlex 2-part liquid silicone set with platinum. It’s a bit expensive, costing me around $30 for enough material to cast a 4 skull mold. But the mold is pretty durable and reusable.
Ceramic bowl (2)
Hot Glue gun & hot glue
Parchment Paper or silpat
Stainless steel mixing bowl (2)
Polymer clay (4 oz)
Strong Double-sided tape or Carpet tape
Disposable brushesâ€¨ (4)
Food Grade Silicone rubber
rice or tapioca pearls (16 oz)
Marked plastic mixing cups (3)
plastic stir sticks (4)
Denatured alcohol (4 oz)
good quality white chocolate (2 lb)
good quality dark chocolate (2 lb)
Heavy whipping cream
Candy melts (14 oz)
Brush the finished surface down with denatured alcohol to smooth it out before baking it. The alcohol melts the clay a bit and will blend in any fingerprints you might have left on the surface of the sculpture. The silicone mold will pick up every detail, including fingerprints, so it is best to take care of this up front, or you will have unappetizing prints all over your chocolates.
Bake the finished skulls according to the directions on the clay packaging. Once baked the clay becomes rock hard and can be sanded or even painted to achieve a smooth finish. I skipped the sanding step since I didn’t think the finished truffles needed to have a glossy sheen.
Make sure the side pieces are deep enough to leave a minimum of 1/4” above the highest point of your original sculpted pieces. Seal all of the sides thoroughly, so no silicone can ooze through the cracks. Have a roll of tape handy in case you need to seal up any leaks that appear when you pour the mold.
Secure the skulls upside-down on the base. You can use double-sided tape, Anchor-Dit (from MYOM) or hot glue like I did. If you care about keeping your originals intact, avoid the hot glue. I didn’t care about them, so I just used what I had. This is a very important step, because the last thing you want is to have your originals break free and float in the silicone. You would then need to wait for it to cure, cut them out and start over with fresh silicone.
Pour the rice or tapioca out of the mold into one of your measured mixing cups. Mark the amount on the cup and you now know how much silicone to mix up. You will need to make a little bit more than this, because the silicone can be thick and will adhere to the sides of your mixing container. You will not be able to get it all out and into your mold.
Brush out your mold and make sure it is clean with no dust or bits of rice or tapioca.
Thoroughly mix a small quantity and brush a skim coat over the pieces to be cast. The point is to embed the silicone in the details so no air bubbles are trapped against the nooks and crannies of the surface, ruining your mold.
Simply chop up whatever quantity of the dark chocolate you want and place it in a bowl. At least a pound is best.
Pour the hot cream over the chocolate and stir until all the chocolate melts.
Roll the chunks between your palms to roughly form them into balls.
Return them to the freezer.
Chop the quantity of chocolate into fine pieces. It helps to make it in batches of close to a pound or more, so the residual heat will keep it in the tempering zone longer.
Scoop 3/4 of the chocolate into a dry bowl or your double boiler. Make sure there are NO drops of water in the bowl or the chocolate will seize up and can’t be tempered. Water and steam are to be kept out of the bowl at all costs or you will need to start over with fresh chocolate.
1) Heat the chocolate pieces in a double boiler to 115°F-120°F to melt the crystals.
2) Add reserved chunks and stir over an ice water bowl until the temperature drops to 85°F-86°F.
3) Place it back over the double boiler in 10 second increments, stirring well until it hits 86°F-88°F It should now be tempered.
Dip a clean knife blade in the chocolate and wait 3-5 minutes to see if it hardens to a satin shell. I have heard that placing the bowl on a heating pad works well to maintain the temperature. I didn’t have one, so I took it on-and-off of the double boiler…constantly stirring and checking to see if I was in that magic zone.
This is the part that was the most difficult. Keeping a bowl of chocolate in a 2 degree window is crazy without the right equipment. In the end, after having to re-temper 4 times, I just crossed my fingers and hoped I had done everything right. I got lucky. If you have the cash, a tempering machine will make this part effortless.
Remove the molds from the feezer and lightly press the bittersweet ganache centers into the center of the cranial area, making sure not to push too far (if you do, the dark center will touch the mold and you will have a dark spot visible on the surface of your white chocolate skull).
Return the molds to the freezer for 5 more min.
Cut the tops flush with a metal spatula and let the truffles set up completely.
The skulls are a bit difficult to remove from the mold, but a gloved finger wedged under the cranium seemed to be the best way to pop them out without any damage.
I had to thin mine out a bit to get them to glaze the walnuts without obscuring the details too much. The brand of candy coating I had called for vegetable shortening, but I added coconut oil, since I don’t use shortening.