Whisk together flour, baking powder, and salt in a medium bowl. In a large bowl, beat butter with both sugars until light and fluffy, about 3 minutes. Beat in eggs one at a time, then mix in ube halaya, ube extract, and vanilla until fully combined and vividly purple. Gradually add dry ingredients and mix just until no flour streaks remain. Cover and chill at least 2 hours or overnight - this is essential for the crinkle effect.

Preheat oven to 350F and line baking sheets with parchment. Scoop dough into 1.5 tablespoon balls. Roll each first in granulated sugar (this creates the crackly barrier), then generously in powdered sugar. The white coating should be thick and opaque - don't be shy here.

Arrange dough balls 2 inches apart on prepared sheets. Bake 10-12 minutes until cookies are puffed, edges are set, and cracks reveal purple beneath the white sugar crust. Centers should still look slightly underdone - they will firm up as they cool.

Let cookies cool on the baking sheet for 5 minutes, then transfer to wire racks to cool completely. The crinkle pattern will deepen as they settle.