In a blender, combine the frozen mango chunks, freshly squeezed lime juice, 1 cup of mango nectar, and ice. Blend on high speed until smooth. As the mixture thickens to a sorbet-like consistency, gradually pour in the remaining mango nectar through the blender lid opening, continuing to blend until fully incorporated. This process should take approximately two minutes.
Prepare the serving glasses by setting up two shallow plates—one with chamoy and the other with chili-lime seasoning. Dip the rim of each 8 oz. glass into the chamoy, ensuring an even coat, then press the coated rim into the chili-lime seasoning for a tangy and spicy crust.
Drizzle a small amount of chamoy (about ½ to 1 tablespoon) into the bottom of each prepared glass. Fill the glass halfway with the mango mixture, then add another layer of chamoy before topping it off with the remaining mango blend. You can swirl the chamoy into the mango mixture using a spoon for a marbled effect or leave the layers visually distinct.
For the finishing touches, garnish each mangonada with fresh mango chunks, an extra drizzle of chamoy, and a sprinkle of chili-lime seasoning. Insert a tamarind straw into each glass, if using. Serve immediately and enjoy this vibrant, sweet-tart, and spicy treat as a cooling refreshment for sunny days.