In a high-speed blender, combine the fresh pineapple chunks, full-fat coconut milk, 1/2 cup water, granulated sugar, fresh lime juice, and salt. Blend until completely smooth and creamy.

Pour the blended mixture into a medium saucepan. Heat over medium heat, stirring occasionally, until it just begins to simmer. Do not bring to a rolling boil.

If a slightly thicker consistency is desired, in a small bowl, whisk together the cornstarch and 2 tablespoons cold water to create a slurry. While the soup is simmering, slowly pour the cornstarch slurry into the saucepan, whisking constantly. Continue to cook and whisk for 1-2 minutes until the soup thickens slightly.

Remove the saucepan from the heat. For an extra smooth texture, carefully pour the soup through a fine-mesh sieve into a clean bowl, pressing down on any solids. Discard any strained pulp. Cover the bowl and refrigerate for at least 4 hours, or preferably overnight, until thoroughly chilled.

Ladle the chilled pineapple coconut dessert soup into individual serving bowls. Garnish with toasted coconut flakes, small diced fresh pineapple, and fresh mint leaves, if desired. Serve immediately.