Thoroughly clean spinach leaves, coarsely chop and set aside.
Dice leeks and crush the garlic bulbs
Melt butter in a large saute pan over medium heat
Add the leeks and garlic, cook until tender but do not brown about 5-8 minutes
Season with salt and pepper
Grate nutmeg over the top
Turn up the heat, and add the spinach in handfuls and salt as you go
Once you can fit it all in the pan, cover and steam until the spinach has wilted, stirring to make sure it does not stick to the pan
Spread cooked spinach onto a platter to cool
Preheat oven to 400F
Once the spinach has cooled, puree the spinach eggs, leeks, garlic, Parmesan and milk in batches
Add extra salt and pepper - the mixture should be heavily seasoned
Pour the batter into a buttered baking dish. Sprinkle the feta over the top
Bake uncovered for 35-45 minutes until firm
The cake is done when tested with a knife and it comes out clean
Serve the spinach cake at room temperature or briefly reheat before serving.