The chocolate garnishes you see on well-made pastries often bear intricate designs that look as if they'd been printed onto the chocolate's surface. They're created with transfer sheets, a pastry chef's version of the colorful temporary "tattoos" children enjoy at birthday parties. The chef paints those designs on acetate strips or sheets with tinted cocoa butter. With patience and a modest degree of artistic skill, anyone can create professional-looking acetate transfers at home.
Trim a sheet of acetate, or cut a roll of acetate, to the size you'll need for your pattern. Set it aside, where it's within easy reach of your work area.
Shave or crumble your cocoa butter into small glass bowls, one for each color you'll be using. Gold, silver, white and red show up best against the brown of the chocolate.
Set the bowls of cocoa butter in a shallow pan of hot water. Stir them periodically as they melt, but take care not to get even a drop of water into the cocoa butter. Water will "seize" the cocoa butter, turning it solid and grainy.
Add powder or paste food colorings to the bowls of cocoa butter in small increments, until you have the shade you want. Don't use liquid food colorings, which will also cause the cocoa butter to seize.
Arrange the bowls of tinted cocoa butter on a heating pad set to its Low setting, which will keep them melted and usable. Use the brush to paint your design on the acetate. Begin with the lightest color, and progress from there to the darkest. Remember, you're creating a mirror image of your design, and it will be reversed when viewed on the chocolate.
Set the acetate aside until the cocoa butter has cooled and set. At that point, the transfer sheet can be used immediately, or stored in the refrigerator for a few days until needed.
You can also make designs in chocolate, thinned with cocoa butter to make it more paint-like. Use white chocolate designs on a dark chocolate surface, and dark chocolate designs on a white chocolate surface.