In a heavy saucepan scald the milk, stir in the chopped mint, and let the mixture steep, covered, for 1 hour. Strain the mixture through a fine sieve set over a bowl, pressing hard on the solids, return the liquid to the pan, and add the sugar and the salt. In a small bowl stir together the cream and the cornstarch. Bring the milk mixture to a simmer, stir the cornstarch mixture, and stir it into the milk mixture. Simmer the mixture, whisking, for 2 minutes, remove the pan from the heat, and stir in the chocolate, stirring until it is melted and the mixture is smooth. Divide the mixture among four 1/2-cup bowls or ramekins and chill the desserts, covered, for 2 hours, or until they are cold. Desserts may be made 1 day in advance and kept covered and chilled. Garnish the desserts with the mint sprigs Serves 4. dess148