There are 2 types of mousse. The first is made with a puree of raw ingredient, eggs and heavy cream which is made in such a way that when the mousse is cooked, it should be very light. This mousse can be consummed hot or cold. The second kind of mousse is made with a puree of cooked ingredient mixed with a cold sauce (i.e. Veloute), dissolved gelatin, and whipped heavy cream. This mousse is simply chilled to "set" the gelatin before serving.