Active time: 15 min Start to finish: 8 1/4 hr (includes chilling and freezing)

　　

Ingredients

Makes about 1 qt

　　1 1/4 cups sugar

　　3 cups water

　　3/4 cup unsweetened cocoa powder, preferably Dutch-process

　　1/4 teaspoon salt

　　1 teaspoon vanilla

　　

Special Equipment

an ice cream maker

　　

Step 1

Cook sugar in a dry 2-quart heavy saucepan over moderate heat, undisturbed, until it begins to melt. Continue to cook, stirring occasionally with a fork, until sugar is melted into a deep golden caramel. Add water (caramel will harden and steam vigorously) and cook over moderately low heat, stirring, until caramel is dissolved.

　　

Step 2

Add cocoa and salt, whisking until dissolved, then transfer to a bowl and cool, stirring occasionally. Stir in vanilla, then chill, covered, until cold (about 2 hours).

　　

Step 3

Freeze in ice cream maker, then transfer to an airtight container and put in freezer to harden.