Name: Fish Casserole
Prep time: 15 min
Cook time: PT-487723H13M39S
Total time: PT-487723H13M39S
Cuisine: American/European
Ingredients: 2 pounds (1 kg) potatoes, peeled and cut into chunks; ¼ cup (1/2 stick) dairy-free butter; ¼ cup plant-based milk; 1 ¾ cups (450 ml) plant-based milk; 2 teaspoons olive oil; 2 green onions, finely sliced; 4 teaspoons (20 g) cornstarch; 1 teaspoon Dijon mustard; ½ teaspoon ground nutmeg; 4 anchovy fillets, finely chopped; 1 ½ cups (400 g) fish pie mix; 2 ½ cups (75 g) baby spinach, roughly chopped; ½ cup (75 g) frozen peas; 3 ½ tablespoons dairy-free butter, divided; Salt and black pepper to taste

Why You’ll Love This Recipe

This casserole is creamy, nutritious, and easy to prepare. The combination of fish, green vegetables, and a flavorful, lightly spiced sauce creates a balanced, hearty dish. Topped with smooth mashed potatoes, it’s a comforting, all-in-one meal that’s perfect for chilly evenings or casual family dinners.

Ingredients

(Tip: Full measurements are listed in the recipe card below.)

For the Mashed Potatoes:

2 pounds (1 kg) potatoes, peeled and cut into chunks
¼ cup (1/2 stick) dairy-free butter
¼ cup plant-based milk

For the Casserole Filling:

1 ¾ cups (450 ml) plant-based milk
2 teaspoons olive oil
2 green onions, finely sliced
4 teaspoons (20 g) cornstarch
1 teaspoon Dijon mustard
½ teaspoon ground nutmeg
4 anchovy fillets, finely chopped
1 ½ cups (400 g) fish pie mix
2 ½ cups (75 g) baby spinach, roughly chopped
½ cup (75 g) frozen peas
3 ½ tablespoons dairy-free butter, divided

Directions

Preheat oven to 375°F (190°C).
Boil potato chunks in salted water until tender, about 15–20 minutes. Drain and mash with ¼ cup dairy-free butter and ¼ cup plant-based milk. Set aside.
In a medium saucepan, heat olive oil and 3 tablespoons dairy-free butter over medium heat. Add green onions and cook for 2–3 minutes until softened.
Stir in cornstarch, Dijon mustard, nutmeg, and chopped anchovies. Slowly whisk in 1 ¾ cups plant-based milk until smooth. Cook until slightly thickened, about 3–4 minutes.
Add fish, spinach, and peas to the sauce. Stir gently to combine and heat through. Adjust seasoning with salt and pepper if desired.
Transfer the mixture to a baking dish and spread mashed potatoes evenly on top. Smooth the surface with a spatula.
Bake in the preheated oven for 20–25 minutes until the top is lightly golden and the filling is bubbling.
Serve hot, garnished with extra chopped green onions or fresh herbs if desired.

Servings and Timing

This recipe serves 4–6.
Preparation time: 15 minutes
Cooking time: 40–45 minutes
Total time: 55–60 minutes

Variations

Use cod, haddock, or salmon for different fish flavor profiles.
Add finely chopped carrots or leeks to the filling for extra vegetables.
Sprinkle breadcrumbs over the mashed potatoes for a crispy topping.
Include a teaspoon of lemon zest or juice for a fresh, bright flavor.
Substitute frozen peas with green beans or broccoli florets for variety.

Storage/Reheating

Store leftovers in an airtight container in the refrigerator for up to 2 days. Reheat in the oven at 350°F (175°C) for 10–15 minutes until warmed through.

FAQs

Can I make this recipe ahead of time?

Yes, assemble the casserole up to the baking step and refrigerate for up to 24 hours before baking.

Can I make it dairy-free or vegan?

Use plant-based milk and butter as listed; for vegan, substitute fish with marinated tofu or chickpeas.

Can I freeze this casserole?

Yes, freeze before baking for up to 2 months. Thaw overnight in the refrigerator and bake as directed.

Can I use fresh herbs in the filling?

Yes, dill, parsley, or chives complement the flavors nicely.

Conclusion

Fish Casserole is a comforting, creamy, and hearty meal that’s perfect for family dinners or special occasions. With tender fish, fresh vegetables, and fluffy mashed potatoes, it’s a versatile, satisfying, and crowd-pleasing dish that can be enjoyed any time of year.