Prepare the Mango Jam by dicing fresh mangoes and placing them in a saucepan over medium heat with white sugar. Stir occasionally for about 10–15 minutes. Remove from heat once thickened and cool completely.

Make the Sticky Rice by soaking sweet rice in water for at least 4 hours or overnight. Drain and steam for 30–40 minutes until tender. Mix in coconut milk and sweetened condensed milk, then allow it to cool.

Prepare the Cookie Dough by creaming butter, brown sugar, and white sugar until fluffy. Add egg and vanilla, then sift in flour, baking soda, and salt. Chill the dough for 30 minutes.

Assemble the Cookies by preheating the oven to 350°F (175°C). Line a baking sheet with parchment paper, scoop dough onto the sheet, add mango jam and sticky rice on each mound.

Bake the Cookies for 13–15 minutes until edges are golden brown and centers are soft. Cool on the baking sheet for 5 minutes before transferring to a wire rack.

Cool the Cookies completely before serving.