Preheat the oven to 180 °C.
Prepare a cake tray with 8 paper cases.
Slice the mushrooms and fry in the butter until fully cooked.
In a bowl, lightly whisk the eggs and milk using a fork.
Chop the feta into small cubes and ham into small squares.
Add the mushrooms, feta, ham and herbs into the egg mix and stir.
Pour the mix into the paper cases up to 80% full (they will rise slightly).
Cook in the oven for 20 minutes at 180 °C.
Eat warm or leave to cool on a wire cooling rack.