Start to finish: 2 hours
2 cups peeled and diced mango (about 1 medium mango)
1 tablespoon cooking oil
1 1/4 teaspoons sugar
1 1/2 teaspoons minced red Thai chili or red jalapeno
Arrange an 11-by-17-inch nonstick silicone mat on a rimmed baking sheet. Heat a food dehydrator to 150 F, or set your oven to its lowest temperature.
Combine all ingredients in a blender, then puree until thoroughly blended, at least 30 seconds. Working quickly, pour the puree onto the mat and use an offset spatula or other long, flat utensil to spread it into an even layer 1/16 inch thick. If the puree sits too long in the blender it may set into a custard-like gel; if that happens, blend it again until it becomes fluid enough that you can spread it easily across the mat.
Place the baking sheet in the dehydrator or oven, and dry until leathery and tacky to the touch. A drying time of 1-1/2 to 2 hours is typical, but the time required can vary considerably depending on the thickness and wetness of the puree layer, the temperature of the chamber, and the humidity of the air. Use the convection setting on your oven if one is available.
When the leather is done, peel it gently from the mat, and use scissors to trim it to individual serving sizes; for use as a garnish, cut it into long, thin strips. To store the leather pieces, roll them individually in waxed paper and then in plastic wrap. The leather will keep for a week when packaged this way.