Preheat your oven to 180°C (350°F). Line a muffin tin with paper liners or grease it lightly.
In a bowl, whisk together the cake flour, baking powder, and salt. Set this aside.
In a separate bowl, beat the softened butter and brown sugar together until light and fluffy. This step matters more than people realise. Properly creamed butter and sugar trap air, which gives your muffins a better rise and a softer texture.
Beat in the eggs one at a time, then stir in the milk, Amasi, and vanilla essence.
Add the dry ingredients to wet ingredients. Mix until just combined. This is the part where overmixing causes problems. Stop as soon as you no longer see streaks of flour. A few small lumps are fine.
Divide the batter evenly between the muffin cups, filling each about two-thirds full. Bake for 18 to 22 minutes, or until a toothpick inserted into the centre comes out clean.
Let the muffins sit in the tin for five minutes before transferring them to a wire rack to cool completely.