Weigh the chocolate: Weigh out the amount of chocolate called for in your recipe. If you aren't following a recipe, start with a small amount and make more as needed.
Measure the cream: Based on the ratio chart above and how you're intending to use the ganache, weigh the amount of cream needed for the ganache in a separate bowl.
Heat the cream: Pour the cream into a small saucepan and place it over medium-low heat for a few minutes. Keep an eye on the cream — it's not necessary to boil or simmer it. It just needs to get hot. The cream is ready when you can place a finger in the cream and keep it there for 3 to 4 seconds. Turn off the flame and remove the cream from the stove.
Chop the chocolate: While the cream is heating, chop the chocolate into fine pieces.
Add the chocolate: Scoop the chocolate into the cream. Stir gently to distribute the chocolate through the cream and then let it sit for a few minutes to give the chocolate time to soften and melt.
Stir the mixture: With a spatula or wooden spoon, stir the ganache. At first it might look spotty and broken but keep stirring until it comes together in a creamy mass.
Cool the ganache: Cool the ganache as specified in your recipe, or as described here:If you plan on pouring the ganache over a cake, pie, or pastry, it will need to be loose enough to flow but thickened enough to stay on the pastry.