Step 1: Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper or lightly grease it.
Step 2: In a large bowl, whisk together the flour, baking powder, sugar, salt, and vanilla custard powder (if using) until well combined.
Step 3: Add the cold, cubed butter to the dry ingredients. Using your fingertips or a pastry blender, cut the butter into the flour mixture until it resembles coarse crumbs with some pea-sized pieces remaining.
Step 4: Make a well in the center of the mixture and pour in the cold Amasi. Mix gently with a fork or your hands until the dough just comes together into a shaggy mass. Be careful not to overmix.
Step 5: Turn the dough out onto a lightly floured surface. Gently knead it just a few times (3-4 times) until it forms a cohesive ball. Do not overwork.
Step 6: Pat or gently roll the dough into a circle or rectangle about 1-inch thick. Using a 2-inch round scone cutter (or a knife for squares/triangles), cut out the scones. Press straight down and lift; do not twist the cutter.
Step 7: Carefully transfer the scones to the prepared baking sheet, spacing them about an inch apart. If desired, brush the tops of the scones lightly with a little extra Amasi or milk for a golden finish.
Step 8: Bake for 20-25 minutes, or until the scones are risen, golden brown, and cooked through. The internal temperature should reach about 200-210°F (93-99°C).
Step 9: Remove from the oven and transfer to a wire rack to cool slightly before serving. These scones are best enjoyed warm.