I want to use a stencil for a design on top of a cake that has a firm chocolate glaze on top. I know I can use cocoa powder sprinkled over the stencil but how can I use real chocolate to create a more solid design ? Would I just use pure chocolate melted or would I make a slight ganache mixture ? Would I have to keep the stencil on until it sets ? How would I get it to set quickly so I don't have to wait a long time ?