Semifreddo is a term used to group a general category of Italian desserts that are served frozen or cold, ranging from various cakes to custards and creams.
Authentic spumoni (not the North American ice cream called spumoni) is an example of a Semifreddo.
The dessert can be based on a custard made with milk, or a custard made with wine, or egg yolk and sugar mixture, or egg whites with sugar syrup mixed with whipped cream and / or custard. Whipped cream or beaten egg whites add air that stop it from freezing overly hard, so that it stays like a frozen mousse.
Whatever the base is, it isn’t churned as gelato or ice cream is.
The entire dessert will often consist of layers of the base with alternating layers of other ingredients. The layers may happen inside a bowl lined with slices of cake. The dessert can be packed into moulds and frozen and then unmoulded and cut to serve, or just scooped out of its freezing container.
“Semifreddo” means “half cold.”