Easy fish pie

I thought up this recipe on Good Friday when I wanted something different to do with the fish. This topping is an easy topping that I often use for moussaka.
white fish fillets, 1 per person
1 small chopped onion
mushrooms, sliced (would be nice with any soft veggies eg patty pans or baby marrow)
1 tin tomato and onion mix
250g greek or natural yoghurt
2 eggs
cheese for sprinkling
salt, pepper, garlic to taste
5ml sugar (optional)

Layer your fish, onions and mushrooms in an oven-proof dish. Pour tomato and onion mix over. Sprinkle garlic, salt, pepper over this. I always add a bit of sugar to my tomatoes when cooking, I feel it brings out the taste. Mix the eggs and the yoghurt thorougly and pour it over the fish. If it doesnt look like the topping is going to cover the base, just spread it around, it really doesnt need to be thick. Sprinkle grated cheese over and put it in the oven at180C until browned and bubbling.
The second time I made it I felt there was too many ingredients for the tomato sauce so I added a cup of chicken stock. In retrospect this was too much, maybe half a cup would have been better, or even less. A little white wine would be nice too. We had it with rice, but nice crusty bread would be good too. I hope you enjoy it if you try it.