The following instructions will help you to compare the taste between different chocolates.
First, use your eyes. The visual qualities that distinguish a fine, well-tempered chocolate include a shine/gleam finish for solid chocolate bars.
Chocolate can range in color from a deep dark brown to a reddish brown. Color depends on the origin of the cocoa beans, how they were roasted and whether they were Dutch processed. Depth of color is not an indication of quality or richness of flavor.
Then, use your fingers. If possible, break off a piece of the chocolate—you should hear a distinct snap (this depends on room temperature as well as the temperature of the chocolate bar). This is the sound of stable crystallization breaking cleanly, which means the chocolate was processed and correctly tempered (i.e., prepared by a specific heating and cooling process).
Hold the piece of the chocolate between your fingers and notice how quickly it melts. Rub your fingers together with the chocolate to test its smoothness. Cocoa butter melts more quickly than sugar so the higher the proportion of cocoa butter, the more quickly it will melt.
Then, use your nose. Lift your fingers with the melted chocolate to your nose and cup your other hand around your fingers in front of your nose. This will help to capture the aromas. It should smell like deep, rich chocolate with floral, fruity or sugary (caramel) aromas—not metallic or medicinal.
Finally, taste the chocolate. Place a small piece of chocolate on your tongue and let it slowly melt. Once the chocolate has melted, run your tongue around your mouth to get the full “mouthfeel” of the texture—it should be full and velvety. As a result of the conching process, fine chocolate will be very smooth compared to cheap chocolate, which may be gritty.
Notice the “finish.” There shouldn’t be a waxy or greasy film left in your mouth after you swallow. Cocoa butter dissipates, leaving only the flavor behind. If that flavor lingers for a while in your mouth, the chocolate is said to have a long finish.