First, add the frozen spinach to a bowl of cold water, and allow to soak for 20 mins. Stir thoroughly to prevent the frozen blocks from clumping together. Then, transfer to a sieve.
Meanwhile, grease 4 large ramekins with butter, and preheat the oven to 200 centigrade.
Heat up the olive oil in a saucepan on a medium heat, then add the lemon zest, red chilli, and red onion, then sweat for 2-3 mins.
Next, add the grated garlic and shredded parsley, stir well, and continue to cook for another 1-2 mins.
Then, squeeze out as much water possible from the spinach in the sieve, and add to the pan. Add the lemon juice, season well with pepper and salt, and mix thoroughly. Transfer the mixture and divide equally into to the four ramekins.
Using the pointed end of an egg, push down into the middle of each each spinach and red onion mixture to form a well, and carefully break the egg so that the yolk sits firmly in the centre.
Drizzle the remaining tablespoon of olive oil over the eggs.
Place on a flat baking tray, and bake for 7-8 minutes.
Remove from oven, add the grated cheese, season well, then return to oven and bake for a further 5-6 minutes.
Serve baking hot.