Makesabout 1 1/2 qt
- Active time:40 min
- Start to finish:2 1/2 hr (includes freezing)
oz Mexican chocolate (3 1/2 disks; preferably Ibarra), coarsely chopped
Halve vanilla bean lengthwise and scrape seeds into a 3-quart heavy saucepan. Add chocolate and half-and-half and bring to a boil over moderate heat, whisking. Remove from heat.
Lightly beat eggs with salt in a bowl, then add hot chocolate mixture in a slow stream, whisking. Transfer custard to cleaned saucepan and cook over moderately low heat, stirring constantly with a wooden spoon, until custard registers 175ºF on thermometer, 1 to 5 minutes. Immediately pour through a fine-mesh sieve into a metal bowl. Put bowl in a larger bowl of ice and cold water and cool, stirring occasionally.
Freeze custard in ice cream maker. Transfer ice cream to an airtight container and freeze until hardened, about 1 hour.
Cooks' note: Ice cream keeps 4 days.