Begin by slicing the passion fruits in half and scooping out the pulp into a bowl. Use a sieve to strain the pulp, extracting about 100-120 ml of tart juice. Next, take your ripe mango and dice it into small pieces before blending until smooth.

In a medium saucepan, combine the passion fruit juice, mango puree, white sugar, and mizuame. Heat on low while stirring continuously, ensuring the sugar dissolves completely and the mixture thickens, about 5-7 minutes.

Gradually pour in the cornstarch slurry (made by mixing 35g of cornstarch with 40g of water) to the simmering mixture. Stir constantly to avoid lumps, and cook until thickened and gooey, around 3-5 minutes.

Once thickened, lower the heat and add the butter, stirring until fully melted and well-combined, about 2-3 minutes.

Line an 8x8 inch baking tray with parchment paper. Pour the mixture into the tray and spread evenly. Allow to cool at room temperature for 1-2 hours until fully set.

After setting, peel off the parchment and place the slab onto a cutting board. Cut into desired shapes and sizes. Optionally roll in granulated sugar before serving.