Step by step

Pour in the oil, then the milk, continuing to beat with the whisk

Tips
When you come to fill the cups with the muffin mixture, which contains baking powder, take care not to do so to more than three-quarters of their capacity. As they cook the muffins will rise, partly overflowing their cups and making them slightly deformed.
Trivia
Feta is a cheese made with sheep's milk. However, you can find this lovely traditional Greek cheese made with 20% goat’s milk.