01 - Preheat oven to 350°F. Line an 8x8-inch baking pan with parchment paper, allowing overhang for easy removal.
02 - In a large bowl, whisk together melted butter, sugar, and ube halaya until completely smooth and uniform.
03 - Add eggs and vanilla extract to the ube mixture, whisking until fully incorporated and the batter is glossy.
04 - In a separate bowl, sift together flour, salt, and baking powder to aerate and remove lumps.
05 - Gently fold the dry ingredients into the ube mixture using a spatula, mixing until just combined. Do not overmix.
06 - In a microwave-safe bowl, melt chocolate with 2 tablespoons butter in 30-second intervals, stirring between each until smooth.
07 - Spread ube batter evenly in the prepared pan. Dollop melted chocolate mixture across the surface, then use a skewer or knife to create a marbled swirl pattern.
08 - Bake for 32-36 minutes until a toothpick inserted into the center comes out with a few moist crumbs attached.
09 - Allow brownies to cool completely in the pan before lifting out by the parchment paper and slicing into squares.