Preparation Steps

• Line an 8x8 inch baking pan with parchment paper, leaving an overhang on the sides.
• In a medium saucepan, combine butter, granulated sugar, and evaporated milk. Cook over medium heat, stirring constantly, until the sugar dissolves and the mixture comes to a boil. Boil for 5 minutes, stirring occasionally.
• Remove from heat. Stir in the white chocolate chips until melted and smooth. Stir in the vanilla extract.
• In a separate bowl, whisk together the custard powder and milk until smooth. Gradually add this mixture to the white chocolate mixture, whisking constantly.
• Pour the fudge mixture into the prepared pan and spread evenly.
• Sprinkle the semi-sweet chocolate chips evenly over the top. Let sit for 5 minutes to soften.
• Gently swirl the melted semi-sweet chocolate chips into the fudge with a toothpick or knife.
• Chill in the refrigerator for at least 2 hours, or until firm. Cut into squares and serve.