Mousse vs Ganache

Mousse is aerated dessert made by folding whipped cream and beaten egg whites into chocolate base creating light fluffy texture with substantial volume. 

Ganache is simply chocolate and cream emulsion, dense and rich without air incorporation. 

The key distinction is air which increases volume dramatically. Proper chocolate mousse should fill two-thirds of serving vessel as dominant layer not thin coating. For six servings use 8 ounces chocolate with 3 eggs and half cup cream creating enough mousse for generous half-cup portions. Thin mousse layer suggests either insufficient aeration from underwhipped components or too little base mixture for number of servings. When folding incorporate whipped cream first to lighten chocolate then fold in egg whites in two additions maintaining as much air as possible. Folding technique matters use gentle cutting motion rather than stirring to preserve airiness. The result should be substantial layer that showcases mousse's characteristic lightness. If mousse layer is so thin it's almost like a ganache the proportions are wrong or it needs to be the star component not supporting player. Mousse deserves celebration with proper volume that demonstrates technical skill.