A gallon-size zip-top bag is the perfect vessel for storing the base while it chills.
Ingredients
Makes about 4½ cups
5
2
1¾
½
⅓
¼
¼
1
3
Preparation
-
Step 1
Set a large metal bowl inside another large bowl filled with ice water. Lightly beat egg yolks in a medium bowl. Bring cream, whole milk, and sugar to a simmer in a medium saucepan. Whisking constantly, gradually stream half of cream mixture into yolks. Return egg mixture to saucepan and cook over medium-high heat, stirring constantly with a wooden spoon, until mixture coats spoon, 2–3 minutes. Strain through a fine-mesh sieve into prepared bowl. Stir in condensed milk and salt. Let cool, stirring occasionally, 20–30 minutes, then stir in buttermilk.
Step 2
Using an immersion blender, mix base until smooth and silky. Add basil; mix until finely chopped. Cover and chill 2 days.
Step 3
Blend base with immersion blender; strain into an ice cream maker. Process according to manufacturer’s directions.
Step 4
Meanwhile, grate chocolate on the large holes of a box grater into a large bowl. Add ice cream and fold to evenly incorporate chocolate. Transfer to an airtight container. Cover and freeze at least 2 hours before scooping.