In medium saucepan over medium-high heat, combine coconut milk, sugar, cornstarch and salt, stirring to dissolve cornstarch. Cook, stirring constantly, until mixture comes to a boil and is smooth and thick, about 5 minutes.
Pour into six 4-oz. molds, or one 3-cup mold. Cover with plastic wrap. Refrigerate until cold and firm, at least 3 hours, or up to 48 hours.
To unmold, run thin knife around edge. Invert mold (or molds) onto serving plate. Top with toasted coconut, if desired. Sprinkle with cinnamon, if desired.
Toasted, shredded coconut makes a deliciously sweet and crunchy topping for all types of desserts, like tembleque, ice cream and more. To toast shredded coconut, heat a toaster oven or conventional oven to 400°F. Spread coconut evenly on sheet pan in a single layer. Cook, stirring occasionally, until coconut turns golden brown and crisp, 7-10 minutes. *Note: The high fat content in coconut can make the shredded pieces go from golden brown to black and charred in minutes. Once the coconut turns light golden brown, remove the pan from the oven and immediately remove the coconut from the hot pan: This will prevent the pan’s residual heat from over-cooking the coconut.