In a medium bowl, whisk together the all-purpose flour, baking powder, and salt. Set aside.

In a large bowl, use a stand mixer with a paddle attachment or a handheld electric mixer. Beat the softened unsalted butter and dark brown sugar on medium-high speed until the mixture is well blended and creamy.

Add the sweetened condensed milk, ube extract, and vanilla extract to the butter-sugar mixture. Continue beating until everything is well incorporated.

Gradually add the dry flour mixture to the wet ube mixture in thirds, beating until no streaks of flour remain. Be sure to scrape down the sides and bottom of the bowl to ensure everything is mixed evenly.

Stir in the white chocolate chips until they are evenly distributed. Cover the bowl with plastic wrap and chill the dough in the refrigerator for at least 3 hours. This helps the flavors meld and the dough firm up.

When ready to bake, preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper.

Scoop about 2 tablespoons of dough and roll it into balls using your hands. Place the dough balls on the prepared baking sheet, ensuring there is about 2 inches of space around each cookie to allow for spreading.

Bake the cookies in the preheated oven for 10-11 minutes, or until the edges are just set but the centers are still soft.

Remove the baking sheet from the oven and allow the cookies to cool completely on the pan. For an optional but recommended step, press a few extra pieces of white chocolate chips onto the top of each cookie immediately after baking for a decorative touch. This will add extra sweetness as well.