Have a timer, heatproof spatula, and six 1-cup custard cups or ramekins near the stove.
In a medium saucepan, combine the cornstarch, salt, milk, and chocolate. Cook over medium heat, whisking continuously and scraping the bottom, sides, and corners of the pan until the chocolate has melted and the first bubbles appear around the edges, 8 to 9 minutes.
Simmer gently, whisking and scraping the pan continuously as the pudding thickens, 2 minutes more, adjusting the heat as necessary to prevent it from boiling furiously.
Immediately scrape the pudding into the custard cups or ramekins.
If desired, top with whipped creambefore serving.