Blend the mango. In a blender or food processor, combine the diced mango, sugar, and lemon juice if you're using it. Blend until the mixture is smooth and creamy.

Freeze the mango puree. Pour the smooth mango puree into a shallow dish and place it in the freezer for about 20-30 minutes.

Combine the dry ingredients. In a microwave-safe bowl, mix together the glutinous rice flour and granulated sugar. Gradually add the water while stirring until the mixture is smooth and free of lumps.

Cook the mochi dough. Cover the bowl with plastic wrap and microwave the mixture on high for 1 minute. Stir, then microwave for another minute. Stir again, then microwave for a final 30 seconds.

Dust a clean surface. Lightly dust your countertop or a large cutting board with cornstarch.

Transfer the mochi mixture. Carefully pour the sticky mochi dough onto the cornstarch-dusted surface. Allow it to cool for a few moments, then dust your hands with cornstarch before dividing the dough into small portions.

Shape the mochi. Take one portion of mochi and flatten it in your hand. Add a small scoop of the frozen mango filling in the center and fold the mochi over it, pinching the edges to seal the filling inside.

Roll into a ball. Gently roll the filled mochi between your hands to form a smooth ball, ensuring the mango filling is completely enclosed.

Chill the finished mochi. Place your completed mango mochi on a plate that’s dusted with cornstarch, and refrigerate for about 10 minutes.

Serve chilled. Enjoy your mango mochi as a refreshing dessert.