Cut the fish into small cubes. Put in a large bowl.
Wash the leeks and chop off any withered or old green leaves. Chop in two lengthwise and slice into medium-thin half-rings. Add to the bowl.
Chop the cheese into dice. Add to the bowl.
Chop the bacon into small squares. Add to the bowl.
In another bowl, beat the eggs with a fork, then add to the large bowl.
Add salt and pepper to taste (remember there’s bacon in there) and mix thoroughly.
Grease a pie plate. Melt butter.
Place at least four sheets of filo onto the pie plate, brushing over with butter between each layer.
Load in the filling. Cover with the another (at least) four layers of filo (or fold over the leftovers from the bottom, if the cover the top). Brush butter over the very top and cut a small knife-hole in the middle.
Bake at 180°C for 40 – 50 minutes until top is golden brown.