Heat up the olive oil in a saucepan over a medium heat. After 2 minutes, add the chopped leek and sauté for 2-3 minutes until softened.
In batches add the spinach and close the saucepan with a lid to allow it to wilt, stirring frequently. Repeat until all the spinach has wilted.
Add this mixture to a bowl along with the rest of the ingredients. Mix until well combined.
Place in an oven safe dish to bake at 180 degrees Celsius fan for 25-30 minutes until lightly golden brown on top and the consistency is perfectly gooey.
