I was recently asked to make a wedding cake, my first one. The brief was a gorgeous impressionist painting of their art-deco home, all geometric shapes in gorgeous pinky hues. I knew that chocolate was going to be a huge part of the cake, but the cake had to survive a 4 hour car trip to Cornwall and then a warm wedding reception room.
The only way to ensure the cake would survive its perilous journey was to make sure the chocolate was well and truly tempered.
Tempering is the action of aligning the cocoa solids in the chocolate so that they are stable. Like a bar of chocolate you buy in the shop. The way to do this is to melt the chocolate and bring it up to a certain temperature before lowering the temperature and then raising it again. Properly tempered chocolate should be glossy and have a snap when broke.
So here is my (almost) fool-proof guide to tempering chocolate.
Measure out 75% of the bar of chocolate you are going to use into a metal bowl. Place on top of a pot of water ( so that the base of the bowl is touching the top of the water. Place a tea towel between the pot and the bowl (this stops any steam from reaching the chocolate and causing the chocolate to seize- chocolate and water are old enemies.)
Turn on the heat, and have at a medium heat. Using a thermometer bring the temperature of the chocolate up to: 55-58c for Dark, 45-50c for Milk, and 45-50c for White chocolate.
Turn the heat off and remove the bowl from the heat, add the other 25% of your chocolate to the bowl (I prefer to grate this part of the chocolate to ensure all of it is melted into the mix). Watch as the temperature drops to: 29c for Dark, 27c for Milk, 26c for White.
Now place the bowl back over the water (do not turn the heat back on- the residual heat will be enough). Watch as the temperature rises back up and take it off when it reaches: D32c for Dark, 30c for Milk and 28c for White.
Pour your chocolate into a piping bag and pipe shapes of chocolate onto pieces of acetate. If you want to cover your chocolate with decorations, do this stage now and fast.. Leave to harden over night and the next morning simply slide the chocolate off with using a spatula. Then using buttercream (the cement of the baking world) stick your shapes to your cake.
Things to be careful of: try to keep your kitchen as cold as possible, prepare all your things in advance, your piping bag/acetate/decorations etc as the chocolate will set very quickly.
If you are unsure if your chocolate is actually tempered dribble some on something metal and wait 5 minutes to see whether its hardened and gone glossy then proceed to pipe your shapes.