Put carob in a medium bowl and whisk in enough coconut milk
(about 2/3 cup) to make a smooth paste. Stir in vanilla. Mix
sugar, cornstarch and salt in a medium saucepan. Gradually
whisk in the remaining coconut milk. Heat over medium heat,
stirring frequently with a wooden spoon or heatproof spatula,
until the mixture begins to barely simmer around the edges.
Then, stirring constantly and scraping the sides and corners of
the pan to prevent scorching, let the mixture simmer for 2 1/2
to 3 minutes to fully cook the cornstarch. Scrape the hot mixture
into the bowl with the carob mixture. Whisk until well blended.
Let cool, undisturbed, for about 45 minutes. Cover and freeze.