• Preheat your oven to 180°C (355°F) and prepare an 8-inch square baking tin by lining it with parchment paper, ensuring the edges extend over the sides for easy removal.
• In a heatproof bowl, combine the butter and white chocolate, and gently melt them using a double boiler or microwave. Stir frequently until you achieve a smooth, glossy mixture. Set aside to cool slightly.
• In a large mixing bowl, whisk together the ube halaya jam, eggs, ube extract, sugar, and salt. Beat until the mixture is smooth and well-combined, creating a rich and vibrant base.
• Gradually pour the cooled butter and chocolate mixture into the ube mixture, whisking constantly to incorporate the two without curdling. Ensure the batter becomes silky and uniform.
• Sift the all-purpose flour over the wet ingredients and gently fold the mixture until just combined. Avoid overmixing to maintain a tender crumb.
• Scatter the white chocolate chunks into the batter, folding gently to distribute them evenly.
• Pour the batter into the prepared baking pan, spreading it evenly into the corners with a spatula. Bake for approximately 30 minutes, or until a toothpick inserted into the center emerges with a few moist crumbs clinging to it.
• Allow the brownies to cool completely in the pan before dusting with purple sweet potato powder, if desired, for a pop of color and flavor.

Make the Icing Drizzle:

• In a small bowl, mix the powdered sugar, milk, and vanilla extract until smooth and free of lumps. If a vivid purple hue is preferred, add a drop or two of purple food coloring and stir until evenly blended. Adjust the consistency by adding more milk for a thinner drizzle or more powdered sugar for a thicker one.
• Drizzle the icing artfully over the cooled brownies, allowing it to cascade naturally for a decorative finish. Slice and serve.