Bring 4 cups of water to a boil in a medium saucepan. Add sago pearls and cook for about 15 minutes until semi-translucent. Remove from heat, cover, and let sit for 15 minutes.

Strain sago through a fine-mesh sieve and rinse under cold water. Soak in cold water for 10 minutes, then drain again.

Peel and dice the ripe mangos, reserving some for garnish. In a blender, combine diced mangos and chilled evaporated milk. Blend until smooth.

In a large bowl, combine cooked sago, remaining mango pieces, optional coconut jelly, and mango jelly. Add blended mango mixture, coconut milk, and condensed milk. Stir well and taste for sweetness adjustment.

Cover and refrigerate for at least 1 hour before serving. Serve chilled in cups or bowls, garnished with reserved mango pieces.