Chop the chocolate into smallish (roughly half an inch or less) pieces.
Find yourself a saucepan big enough to hold all of your cream and chocolate, and weigh the cream straight into it. Place the pan over a medium-high heat and bring it just to a boil. The bubbles should cover most of the cream's surface. Make sure you watch it carefully, once it comes to the boil it can quickly boil over. Remove from the heat and leave it until the bubbles stop.
Add the chopped chocolate to the pan, and gently shake the pan until the chocolate is mostly covered by the cream. Don't stir it yet, just leave it to sit and melt for a few minutes.
Gently stir with a silicone spatula (or use a wire whisk for dark chocolate ganache, as it is softer). Keep stirring until the chocolate and cream fully combine and become smooth.
If there are still unmelted pieces of chocolate in the ganache, place the pan back over a very low heat, and stir constantly until no lumps remain and the ganache is glossy and smooth.
If you happen to own a stick mixer/hand blender, then you can use that to give the ganache a quick blitz to ensure all the chocolate is melted and that the emulsion is smooth.If you want to colour the ganache, you can do that now.
Pour the ganache into a microwave-safe bowl, leave to cool then cover with plastic wrap on the surface of the ganache and leave overnight at room temperature to set.
If you don't have time to let the ganache set at room temperature then you can speed it up by putting it in the fridge - just make sure you stir it often so that it cools and sets evenly.
You can store the ganache at room temperature for a couple of days, or refrigerate it for a month or so, or freeze it for a little longer. These time frames are an indication only and could vary depending on the ingredients used and storage temperatures, so you will need to use your discretion when storing.
Notes
Depending on the weather you may need to increase or decrease the amount of chocolate to get a ganache that sets correctly.Use the Ganacherator to work out how much ganache is needed for the specific-sized cake you're making.Example for calculating ingredient amounts: for an 8″ round cake with four layers of cake (and therefore 3 layers of ganache filling) you would need approximately 1800g (1.8kg) of ganache to fill and cover it.Dark chocolate ganache is a 2:1 ratio, which is 3 ‘parts’ in total. To work out how much chocolate and cream you need, you just divide 1800g by 3, which is 600g, so that is how much cream you need (one ‘part’ cream) and you need twice as much chocolate (2 ‘parts’ chocolate), so 600g times 2 is 1200g.So for 1800g of dark chocolate ganache, you will need 1200g of chocolate and 600g of cream.Cream - The type of cream you need for ganache is known by different names in different countries. In New Zealand, we usually call it regular cream or whipping cream, in other countries it may also be known as standard cream, single cream or full cream. Heavy whipping cream and thickened cream (common in Australia) should also work in this recipe. Long story short? You need a pourable, unsweetened, unwhipped cream that is around 35% fat.What to do if your ganache splits:Split (or broken) ganache is when the chocolate and cream don't emulsify properly. It will look a bit dull and slightly grainy. You may also see the oil separating from the cocoa solids. But don't panic! In most cases, you should be able to save it.
The first thing to try to correct it is to use a stick mixer/hand blender, just place it in the ganache and blend it until the ganache has come together and is smooth. Once it is smooth, stop blending, otherwise, you will incorporate too much air.
If that doesn't work, there are a couple more things you can try. The first is to add a splash more cream and mix, this may bring the ganache back together. You may need to add even more cream, in which case just bear in mind that your ganache will not set as firmly.
You can also try popping the ganache into the fridge, stirring every 10 minutes or so, and the ganache may emulsify again.