What you will need:
A packet of mixed seafood, precooked (I used a 500g packet)
1 onion
Approximately 1 ½ dessert spoons of flour (either plain or self-raising)
Approximately 1-1½ small cups of milk (I used low-fat but full-fat would work too)
5 large potatoes (if you like a lot of potato on your pie then use 2 more, but this was enough to fill the dish above)
Salt and pepper to season
Chilli powder (optional)
Grated cheese for the top of the pie (optional)