Makes about 3 1/2 cups
1 1/2 cups heavy whipping cream
1 cup whole milk
1/2 cup cacao nibs*
1/2 vanilla bean, split lengthwise
5 large egg yolks
3/4 cup sugar
* Bits of shell-roasted cacao beans; available at many specialty foods stores and from chocosphere.com.
SPECIAL EQUIPMENT: Ice cream maker
Step 1: The ice cream custard needs to infuse with the flavor of the cacao nibs overnight, so start preparing it two days ahead. Serve along side Layered Brownies with White-Chocolate Caramel and Cacao Nib Gelato.
Step 2: Combine 1 1/2 cups heavy whipping cream, 1 cup whole milk, and 1/2 cup cacao nibs in heavy large saucepan.
Step 3: Scrape in seeds from 1/2 vanilla bean; add bean. Bring mixture to simmer. Remove from heat. Cover and let mixture steep 30 minutes. Uncover and return to simmer.
Step 4: Whisk 5 large egg yolks and 3/4 cup sugar in large heatproof bowl until mixture is pale yellow and slightly thickened.
Step 5: Gradually add hot cream mixture to yolk mixture, whisking until well blended. Return mixture to same saucepan and stir over medium-low heat until custard thickens and coats back of spoon when finger is drawn across and instant-read thermometer inserted into custard registers 170°F, about 5 minutes (do not boil).
Step 6: Transfer custard to medium bowl. Cover and chill overnight.
Step 7: Pour custard through fine strainer set over bowl; discard solids in strainer.
Step 8: Transfer custard to ice cream maker and process according to manufacturer's instructions.
Step 9: Transfer gelato to freezer container. Cover and freeze until ice cream is firm, at least 8 hours or overnight.
Step 10: DO AHEAD - Can be made 3 days ahead. Keep frozen.