Move over shepherd’s pie and make way for the fisherman’s version, the fish pie! This low-carb version of this classic British dish is chock full of omega-3s with a combination of mackerel and smoked herring, as well as shrimp and not-so-traditional chopped greens for added texture and nutrition. I used mashed rutabaga mixed with cheese for the topping, making this dish a delicious seafood medley in a casserole-style presentation.

Keto Cheesy Fish Pie

Filling Ingredients:

Topping Ingredients:


  1. To make the filling, pour your chosen milk into a large lidded pan and add the diced onion and bay leaves. Season with salt and black pepper. Bring to a very gentle simmer then add the shrimp, cover with a lid and remove from the heat immediately. Leave to stand and infuse for 10 minutes until the shrimp is just cooked. Strain the shrimp, garlic and onions using a colander, draining the milk into a heat-safe bowl. Whisk glucomannan into the milk.(*Note: If you want to use fresh fish instead of canned, add the fish to cook with the shrimp.)

  2. While the milk is standing, make the topping. (*Note: The potato is not to be eaten, boiling the rutabaga with it gets rid of the bitter taste of the turnips while they are cooking.) Add water until the rutabaga is fully covered. Add salt and bring to a boil. Reduce heat to medium and cover. Cook for about 15-17 minutes or until rutabaga is fork tender.

  3. While the rutabaga is cooking, steam the chopped kale for 3 minutes in a pot with a little water or in a steamer in an Instant Pot. Remove from heat and rinse with cold water. Set aside.

  4. Reheat the pot to medium heat. Return the drained rutabaga, removing the potato, then return to the pot and heat for 1-2 minutes to cook off any excess water so it absorbs all the other ingredients. Stir gently to make sure all the rutabaga pieces dry out. Remove from heat.

  5. Heat the butter and milk in the microwave or in a pot until steaming. Add to the pot with the rutabaga and mash until smooth. Stir in ¾ of the grated cheese then season to taste with salt and black pepper.

  6. Preheat the oven to 400F. To finish the filling, melt the butter in a medium saucepan and whisk in the oat fibre. Cook for a few seconds until frothy then add the infused milk a little at a time, stirring constantly, and simmer over a medium heat for 3–4 minutes until the sauce is smooth and thick. Remove from heat then stir in the mustard, cooked leafy greens smoked herring, mackerel, shrimp and onions. Season with salt and black pepper to taste.

  7. Add the filling to a 3-quart casserole dish (or two smaller dishes if you want to cover and freeze one to be cooked at a later time).

  8. Spoon the mashed rutabaga over the fish mixture, spreading to the edges with a rubber spatula. Sprinkle over the remaining cheese. Place the dish on a baking tray and bake in the centre of the oven for about 25-30 minutes or until the top is golden-brown and the filling is bubbling. Remove from oven and allow to set 7-10 minutes before spooning and serving.

Did you make this keto cheesy fish pie recipe? If so, please let me know how it turned out in the comments. Or if you share pics of your creations on Instagram, please tag me so I can see them. Enjoy!