Mascarpone is an Italian cream cheese; this is like having a cheesecake-flavored gelato.
In a medium saucepan, heat milk and vanilla bean and scrapings. Bring to a gentle boil, cover, and remove from heat. Steep for 30 minutes.
Combine egg yolks and sugar in the bowl of an electric mixer. Beat at medium-high speed until very thick and pale yellow, 3 to 5 minutes. Meanwhile, return milk to a simmer.
Remove vanilla bean. Add half the milk to egg-yolk mixture and whisk until blended. Stir into remaining milk and cook over low heat, stirring constantly, until mixture is thick enough to coat a spoon.
Remove from heat and immediately stir in cream. Pass mixture through a strainer into a medium bowl set over an ice bath to chill. Whisk in mascarpone until completely blended, then freeze in an ice-cream maker according to manufacturer's instructions. Store in a plastic container.
Many Italians eat this gelato affogato, or "drowned." To do so, pour a cup of hot espresso over a scoop before serving.