In a small bowl, combine the sweetened condensed milk, granulated sugar, water, and vanilla extract. Whisk until sugar is dissolved and mixture is smooth. Taste and adjust sweetness; set aside in the refrigerator to chill while you prepare mangoes and ice.

Prepare Mango Topping

Dice mangoes

Peel and pit fresh ripe mangoes. Dice enough to yield about 2 cups of mango cubes. Reserve a few larger pieces for garnish if desired.

Optional mango puree/syrup

If using mango puree, place 1 cup diced mango (or fresh/frozen mango) into a blender with the lime juice and optional 1 tsp sugar. Blend until smooth. Taste and adjust lime/sugar. If texture is too thick, add 1-2 tbsp water. Chill until ready to assemble.

Shave Ice and Assemble

Shave the ice

Using a dedicated ice shaver or a high-powered blender/food processor fitted with a blade, shave the ice cubes/blocks into fine snow-like ice. Work in batches to avoid melting. Transfer shaved ice to a bowl and fluff with a fork to remove clumps. Aim for very fine, powdery ice for the best texture.

Sweeten the shaved ice

Place about 1/4 to 1/3 cup of the chilled sweetened milk mixture over each serving of shaved ice (adjust to taste). Gently toss or press so the condensed milk soaks through some of the ice, but keep much of the fluffy texture.

Add mango topping

Spoon a generous portion (about 1/2 to 3/4 cup) of diced mango over each sweetened shaved ice mound. Drizzle 2-3 tbsp of the mango puree (if using) over the top to create a syrupy layer and extra mango flavor.

Garnish and serve

Finish with a small drizzle (about 1 tbsp) of additional condensed milk on top if desired, sprinkle toasted coconut or shredded coconut, and add a mint leaf for color. Serve immediately with a spoon to preserve the fine texture of the shaved ice.