Preheat oven to 180°C/350°F (160°C fan) for 20 minutes before starting the batter.
In a large bowl, whisk flour, baking powder, sugar and salt and set aside.
Place butter and milk in a heatproof jug and microwave for 2 minutes on high until melted.
In a separate bowl, beat your eggs and oil until fluffy and light in colour.
When the egg is whipped, beat in the milk and oil in slowly.
Add your wet ingredients to your dry ingredients and beat until fully incorporated. Scrape down sides, your batter should now be smooth and pourable.
Pour the batter into your muffin cases, filling 2/3 of the way up.
Bake 22 minutes or until golden and toothpick inserted into middle comes out clean.
Remove from oven. Cool for a couple of minutes, and then remove and place on a cooling rack. Cool completely before icing with frosting.