Place chocolate and butter in a heatproof bowl that fits snuggly in a saucepan (this stops water spraying into the chocolate). Half-fill saucepan with water and bring to a simmer. Place bowl on top, making sure it doesn't touch water (or it will overheat). Stir with a metal spoon until melted. Avoid wooden or plastic spoons as these retain moisture that makes chocolate seize (harden).
Remove bowl from heat, allow to cool slightly, then stir in the egg yolks and McCormick Spices. Continue stirring until the mixture thickens.
Place in a refrigerator for approximately 1 hour or until the mixture has set.
Once mixture has set, roll into 1 teaspoon sized balls and roll in cocoa powder.
Add finely grated zest of ½ orange to truffle mix for added zing and flavour.