In a medium saucepan, cook 200g of frozen mangoes over medium heat, stirring constantly until they start to break down. Mash them gently with a fork, then add 1 tablespoon of white sugar. Continue stirring until the mixture thickens into a jam-like consistency, about 5-7 minutes. Transfer to a bowl and let it cool in the fridge while you prepare the next steps.

Rinse 0.25 cup of sweet rice under cold water, then soak it in boiling water for 20 minutes. After soaking, drain the water, place the rice in a steamer lined with cheesecloth, and steam for about 25-30 minutes until tender but slightly underdone. Once done, combine the sticky rice with 0.33 cup of coconut milk and 3 tablespoons of sweetened condensed milk, setting aside 1 tablespoon of the mixture for later.

In a large mixing bowl, cream together 113g of softened unsalted butter with 100g of light brown sugar and 50g of white sugar until fluffy and light in color. Stir in one large egg yolk and the thick egg white, followed by 0.5 teaspoon of vanilla extract and the reserved 1 tablespoon of coconut cream. Mix well to combine all the flavors into your Mango Sticky Rice Cookies dough.

In a separate bowl, whisk together 180g of all-purpose flour, 0.5 teaspoon of baking soda, and 0.25 teaspoon of salt until well blended. Gradually fold these dry ingredients into the wet mixture, stirring until just combined. Be careful not to overmix, as this could affect the texture of your Mango Sticky Rice Cookies. Chill the dough for 30 minutes in the refrigerator to firm up.

Preheat your oven to 350°F (175°C) and line a baking tray with parchment paper. Gently swirl together portions of the sticky rice mixture and mango jam into the cookie dough, ensuring an even distribution. Use a scoop to portion the dough onto the prepared baking tray, spacing them about 2 inches apart. Optionally sprinkle with flaky sea salt or black sesame seeds for added flavor.

Place your tray in the preheated oven and bake the Mango Sticky Rice Cookies for 13-15 minutes, or until the edges are golden brown and the centers appear set. Once baked, allow the cookies to cool on the tray for about 10 minutes before transferring them to a wire rack to cool completely, letting their flavors develop as they rest.