Simple Spreadable Ganache
I discuss a ratio of 2:1, chocolate to cream in this recipe. This applies to dark or semisweet chocolate. If you are working with milk chocolate or white chocolate, a ratio of 3:1 gives best results. ****You can also whip this ganache to create a whipped ganache filling--it is less perishable than our chocolate mousse filling and is fine to leave at room temp for a day or two. It will be a thick consistency.
If you'd like a softer ganache, use a 1:1 ratio of chocolate to cream rather than 2:1 (referring to semi-sweet or dark chocolate). Equal parts of chocolate to cream will make it more perishable but will give you a softer consistency. I use this 1:1 consistency for chocolate drip cakes.
Simple Spreadable Ganache Frosting:
I usually use dark chocolate chips with at least 53% cocoa for my frosting. The key with this ganache is that you want a 2:1 ratio of chocolate to heavy whipping cream. For example, if you have 2 lbs of chocolate, you will need 1 pound of cream. You will need to measure by weight.
Let your cream become very hot over medium heat. Turn the heat off just as the cream comes to a boil and pour in the chocolate. Let it sit for a couple of minutes (to soften the chocolate). Stir and keep stirring until chocolate and cream are smooth. If you find that you still have a few chocolate bits unmelted, you can use an immersion blender. You shouldn't have any chocolate pieces floating around.
At this point, your ganache will be runny. Allow to cool to room temperature, whenever I try to speed up the cooling process by putting the ganache in the refrigerator while still warm -- the ganache never sets up correctly, so I let it cool over several hours at room temperature. Putting the ganache in a large, shallow casserole dish will speed things along. It will cool during several hours or overnight and become spreading consistency. This consistency is much like peanut butter. If you are not ready to use it at this point, it can be refrigerated. Press plastic wrap onto the surface of the chocolate, you don't want condensation to form and the water droplets to fall into the chocolate. We have refrigerated ganache for two weeks with no problem. It can also be frozen for 3 months, maybe longer, but we haven't tested beyond that time. You can always do a taste test, because if the cream in the ganache has gone bad you definitely know by tasting.
I usually have to do two coats of ganache in order to ensure that everything is covered. Another alternative would be to frost your cake with a thin coat of buttercream first, and then follow with a coat of ganache frosting. Use a hot spatule for a very smooth finish. **IF MAKING A WHIPPED GANACHE FILLING, SEE BELOW.
**If you are whipping the ganache for a filling....
After allowing ganache to cool to room temp, and chilling the ganache, it may become too firm to whip. If this happens, warm in the microwave in 10 second intervals (stirring each time) until it is the right consistency. The mixture must be slightly chilled at the time of mixing in order to whip properly. I would whip on medium speed.