1. In a big pot boil the potatoes in salted water for 20 minute.
2. In a large sauce pan melt the butter and the flour whisk the mixture to get a roux consistency then add the salt & pepper followed by milk, the sauce should be nice and thick.
3. Add parsley which is snipped to the sauce and stir well.
4. In a greased tray place the fish and then pour some of the sauce over the fish.
5. Now check on the potatoes and once cooked then drain the water and mash the potatoes and get rid of all the lump.
6. Add milk to the potatoes and whisk well and keep it aside.
7. Now layer the mash over the fish covering all the corners and then put grated cheese and sliced tomatoes on top.
8. Cook the fish in the oven for 30 minutes at 200 degree C.
9. Serve with cherry tomatoes and parsley sauce.