For a standard 8-inch round cake (4 inches tall with 3 sponge layers and 2 filling layers), you need approximately 800g to 850g of total ganache. If using dark chocolate for sharp edges (2:1 ratio), combine 550g dark chocolate with 275g heavy cream (35% fat). If you only need to coat the exterior without filling between layers, 450g to 500g is sufficient.

White chocolate contains no cocoa solids and high amounts of cocoa butter and dairy fat, requiring significantly less cream. While dark chocolate uses a 2:1 ratio for firm crumb coats, white chocolate requires a 3.5:1 or 4:1 ratio (350g–400g white chocolate to 100g cream) to set firmly enough for sharp edges and warm room temperatures.

Ganache splits when the cream is overheated or the ratio of fat to water is exceeded, causing cocoa butter to separate from the liquid. To rescue it: warm 1 to 2 tablespoons of whole milk or cream to 40°C (104°F), add it to the center of the bowl, and vigorously whisk in small circles until the emulsion re-forms, then blend outward.

Whipped ganache requires a higher proportion of liquid cream to allow air entrapment. For dark chocolate, use a 1:2 ratio (100g chocolate to 200g cream). Chill the mixture for at least 6 hours at 4°C (39°F) so the fat crystallizes, then whip on medium speed until soft, velvety peaks form. Do not overwhip or it will turn grainy and split into chocolate butter.