Prepare Filling & Boil Potatoes

1. Preheat oven to 350º
2. Place the fish fillets skin-side-down in a foiled-lined and oiled pan
3. Bake 10-15 minutes, or until flaky
4. Meanwhile, bring a large pot of water to a boil. Add potatoes and boil 15-20 minutes, or until cooked through. Drain and set aside
5. Heat canola oil over medum-high in a medium sauté pan. Sauté onion about 5 minutes, or until soft. Set aside
6. Remove skin from the fish and break the fillets up into small pieces using a fork. Transfer to a large bowl with the onions
7. Add the peeled shrimp and stir to combine
8. Spread evenly in a baking dish and set aside

Make Sauce

1. Melt the butter in a medium pot over a medium-low heat. Slowly mix in flour to make a paste
2. Gradually add the milk, stirring constantly to avoid any lumps
3. Once the sauce is smoothly mixed and hot, add the grated cheese, stirring constantly until the cheese has all melted and the sauce is smooth. Add salt and pepper if desired
4. Pour evenly over the fish mixture, making sure the fish is coated (but not too submerged, as the sauce will bubble up as it cooks)

Make Potato Topping & Bake

1. Raise oven temperature to 375º
2. Mash the drained, cooked potatoes with butter (add more or less as desired), and slowly mix in milk. Use as much as is needed for a creamy, yet firm topping. Stir in heavy cream. Season with salt and pepper if desired
3. Spoon over the fish and sauce mixture and then spread evenly to the edges of the pan
4. Bake, uncovered for 40-45 minutes, or until the potato crust has turned golden brown
5. Allow to cool slightly, then serve with green vegetables or salad and crusty bread (to mop up the sauce!)