Fish pie with mustard mash

Warm & comforting fish pie, with gooey sauce & creamy, mustardy mash, is a wonderful, nutritious family dinner. Prepare in advance for an easy midweek meal.

Sometimes, things don’t go exactly as you had hoped. This fish pie was just such an occasion. Despite years of fish-pie-making experience, the sauce came out lumpy and needed to be blended smooth, I got covered in fish scales, and the pan of potatoes boiled over. Then, when I assembled the pie, the dish wasn’t big enough and I spilled sauce everywhere. By the time it went into the oven I was ready to give up and just have toast for dinner. 

The future’s bright!

Apparently, I should have been more optimistic. After a sit down, a deep breathe and a clear up, a delicious aroma was starting to fill the kitchen. By the time the fish pie had baked to golden loveliness in the oven, it actually looked pretty appetising. More importantly, it tasted awesome!

Make it in advance

This is another recipe in the ongoing series of ‘dishes that can be made in advance and left to cook by themselves in a pre-set oven’. You can assemble it all the way up to topping it with the mash, then leave it to cool and bake it when you’re ready. You can even freeze it at this point! Of course if you’re baking it from cold it might take a little while longer in the oven. You need to make sure that the filling is completely piping hot, all the way through.

In praise of fish pie

I really love fish pie, especially when the weather is cold or grey. It’s warm and comforting, smothered in a blanket of creamy mash and gooey with sauce. I like to include some smoked fish in the mix, which adds an extra layer of delicious flavour. In this recipe I used dill in the sauce and mustard in the mash, but you can change up the seasonings according to your preferences. 

Top tips!

My top tips for fish pie making are as follows:

  • Always use more fish than you think you’ll need – I used to put in one portion of fish per person, but this seemed to never be quite enough. 
  • Likewise with mash – more is better.
  • Don’t make the sauce too thick – it will thicken up in the oven. In any case, the contrast of runny sauce and thick, creamy mash is wonderful.
  • Make sure the mash gets crispy on the top. It’s sometimes necessary to give the fish pie a quick go under a hot grill to achieve this, but it’s definitely worth it. 

Armed with this knowledge, and the recipe below, hopefully you’ll have a better fish pie making experience than I did. With a similarly delicious end result. 

Serves 3-4.

Fish pie with mustard mash

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Fish pie with mustard mash

Course Main Course
Cuisine British
Keyword fish, potato
Prep Time 45 minutes
Cook Time 45 minutes
Total Time 1 hour 30 minutes
Calories 475kcal
Author Helen


For the filling

  • 150 g haddock fillet (or other white fish) (5¼ oz.)
  • 150 g smoked haddock fillet (5¼ oz.)
  • 250 g salmon or trout fillet (8¾ oz.)
  • 25 g butter (1¾ tbsp)
  • 2 tbsp flour
  • 500 ml milk (2¼ cups)
  • 2 tbsp finely chopped fresh dill

For the mash

  • 850 g potatoes (1 lb 14 oz.)
  • 50 ml milk (¼ cup)
  • 1-2 tsp wholegrain mustard


  • First, cook the potatoes. Peel them, then cut into 1-2cm dice. Cover with cold water and bring to the boil. Simmer for 10-15 minutes until very soft.
  • Meanwhile, prepare the fish. Skin the fillets if necessary and remove any remaining bones. Cut the fish into chunks and set aside.
  • Make the sauce - melt the butter in a large heavy based pan, then stir in the flour and cook for a minute, stirring all the time. Gradually add the milk, stirring well to ensure a smooth sauce. Once all the milk is added, continue to cook, stirring continuously, until the sauce come up to the boil and thickens slightly. Remove from the heat.
  • Gently stir the chopped dill and prepared fish pieces into the sauce. Cover with a lid and set aside.
  • Make the mash. Drain the cooked potatoes and mash well with the milk and mustard to give a creamy consistency. If necessary, add a drop more milk.
  • Preheat the oven to 180°C (350°F).
  • Assemble the pie. Use a slotted spoon to gently transfer the fish from the sauce into a pie dish. Spread the fish in an even layer, trying to mix up the different sorts of fish. Very carefully, pour the sauce over, trying to avoid disturbing the fish pieces.
  • Arrange the mashed potato on top of the fish and sauce, and use a fork to rough up the surface. Place the pie dish on a baking tray and transfer to the oven.
  • Cook at 180°C (350°F) for 30-45 minutes, until hot throughout and browning on top.


475 calories, 13g fat, 40g protein, 48g carbs

If you want the flavour of a fish pie but with a bit less faff, try this fish pie pasta bake instead!

fish pie with mustard mash


  1. Love the sound of mustard mash.
    My kids adore fish pie

  2. Have to admit I rarely make fish pie as it seems like a faff sometimes, looks like yours was totally worth it though. Love the sound of the mustard mash on top.

  3. Ooh yum! I love fish pie, one of my favourites but I haven’t made it for ages! You have inspired me!

  4. Looks delicious and the mustard mash sounds really tasty!

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