Decorating cupcakes with chocolate is lots of fun and there are so many different ways that chocolate can be used to achieve many different effects.
The most important step when using chocolate for cupcake decorations is melting it. You can either use a bowl over steaming water or a microwace to melt chocolate. If using a microwave, I would recommend using half heat for 30 seconds at a time until melted.
My favorite chocolate decorations are:
Frost cupcakes. Put melted chocolate in a piping bag. Holding the piping bag 5cm (2in) above cupcakes, pipe lines by gently squeezing the bag. This looks great if the chocolate is a contrasting colour to the frosting. cupcakes with piped chocolate
Put melted chocolate in a piping bag. Pipe designs onto a sheet of greaseproof paper and leave to set. Carefully remove each design. If you want each design to be identical you could copy designs on to blank paper and place the greaseproof paper over the drawing sheet.
Use different blades of a grater to achieve different textures. Grated chocolate can be used to cover the sides of cupcakes. I often use a potato peeler to get a different texture.
Spread melted chocolate on to greaseproof paper or plastic wrap. Leave to set. When set, break into pieces. This can be used for the side or top of cakes.
Spread melted chocolate on to work surface. Leave to set. When set, use the blade of a knife and draw it at a 45 degree angle across the surface to remove a thin layer. Refrigerate the curls until you are ready to use them as they can lose their shape on standing.
Spread melted chocolate on to greaseproof paper. Leave until set. Press out shapes with cutters. Carefully remove each cut-out.
Gently wipe leaves with a damp cloth. Melt chocolate. Use a paintbrush to brush the underside of each leaf with chocolate. Chill until set. Carefully peel each leaf away from chocolate.
Lately, when I have been decorating cupcakes for birthday parties I have used a dark or white chocolate button and piped either the initial of the birthday person or their age with the corresponding chocolate.
I recently piped dark chocolate onto a white chocolate button for a 40th birthday and added a slice of strawberry which was really suitable for an informal picnic party.