Place all but ¼ cup of the mangoes and the lime juice, sugar, and water in a blender and blend until smooth. Add the ice and tequila and blend to a slushie consistency. Taste, adding more tequila if you like. Pour into a lidded container and place in the freezer for 30 minutes.

To serve, spoon a tablespoon or 2 of chamoy into the bottoms of each of four glasses, then sprinkle with a pinch of tajin. Pour about ½ cup of the mango slushie on top. Repeat with another tablespoon or 2 of chamoy, tajin, and mango slushie until the glasses are full. Top with another sprinkle of tajin. Garnish with the remaining ¼ cup mango cubes and tamarind candy straws.