Derek Poirier, one of Canada's finest pastry chefs gave some of the following advise recently to Amy Sherman (from Cooking with Amy). I'm going to test his technique and see how it holds up to mine and get back to everyone.
He explained that ganache is an emulsion because cream is mostly made of water and chocolate is mostly comprised of fat. The taste test of ganache made with melted versus non-melted chocolate made everyone a believer. In addition to impressing the heck out of me by using a laser thermometer, here is what I, as a non-professional learned from Chef Poirer:
1. In order to make the best tasting and most stable ganache, use the rules for any emulsion, make sure both the chocolate and the cream are warm (35 degrees Celsius is the fusion point). This means you need to melt the chocolate before combining it with the cream and to beat it vigorously with a hand blender to emulsify it.
2. In order to fix a broken ganache, heat the base if the temperature was too low, and add more cream if the temperature is fine.
3. When beating cream or egg whites, do so at 3/4 speed, not full speed. Why? Smaller bubble structure will lead to less collapse and better texture.