Chop the chocolate. The finer the chop, the easier it will be to get it to melt. Quarter-inch chunks are fine. Put the chopped chocolate in a glass bowl. Heat the cream on medium high in a sauce pan on your stove top. Be sure to keep an eye on the cream for when it hits the boiling point. This only takes a minute or so. When bubbles form around the edges, it's just about ready. You don't want to let it boil over.
Pour the hot cream over the chocolate. Have your whisk ready and start to stir. Keep stirring until all the chocolate is melted and the mixture is a smooth, dreamy dark color. This GLAZE is ready to use now if you want it runny and warm.
If you want to FROST a cake, wait until the ganache cools down. (Do not refrigerate.) Depending on the temperature of your kitchen, this might take a few hours. Just walk by and stir it every half hour or so and you'll be able to see when it's ready. If you wait too long, it will start to turn to a candy-bar consistency and it will get too firm to spread. If this happens, just zap it in your microwave for 15 seconds to get it to loosen and then start again keeping an eye on it.
If you want, you can whip ganache so it's fluffy. You have to be careful just to whip it until it's light. If you whip it too long the cream will turn to butter and it gets gloppy. WHIPPED GANACHE will be a lighter brown.
After you frost your cake with the glaze, the frosting, or the whipped ganache, you can store it in the refrigerator. The ganache will stiffen. You can then lay decorations on the cake without fear that they will stick. Bring the cake out of the refrigerator a few hours ahead of serving to bring it back to room temp.
The ganache will only remain glossy as long it's warm. As it hardens, it looks more like a Hershey bar.