Keto fish casserole with mushrooms and French mustard

• 1 lb mushrooms
• 3½ oz. butter
• 1 tsp salt
• pepper, to taste
• 2 tbsp fresh parsley
• 2 cups heavy whipping cream
• 2 tbsp Dijon mustard
• 8 oz. shredded cheese
• 1½ lbs white fish, for example cod
• 1½ lbs broccoli or cauliflower
• 3½ oz. butter or olive oil

Instructions

1. Preheat the oven to 350°F (175°C).
2. Cut the mushrooms into wedges. Fry in butter until the mushrooms have softened, about 5 minutes. Add salt, pepper, and parsley.
3. Pour in the heavy cream and mustard and lower the heat. Let simmer for 5-10 minutes to reduce the sauce a bit.
4. Season the fish with salt and pepper and place in a greased baking dish. Sprinkle 3/4 of the cheese on and pour the creamed mushrooms on top. Top with the remaining cheese.
5. Bake for about 30 minutes if the fish is frozen, or slightly less if it’s fresh. Probe with a sharp knife after 20 minutes; the fish is done if it flakes easily with a fork. And remember that the fish will continue to cook even after you have taken it out of the oven.
6. Meanwhile, make the side dish. Cut the broccoli or cauliflower into florets. Boil in lightly salted water for a few minutes. Strain off the water and add olive oil or butter.
7. Mash coarsely with a wooden spoon or fork.
8. Season with salt and pepper and serve with the fish.