Serves 4; can be doubled.
Ingredients
1 lb halibut or other white fish (cod, scrod, haddock, or a mix)
1 tsp Old Bay Seasoning
Kosher salt and fresh black pepper
3 Tbsp butter, divided
2 Tbsp olive oil
1 small onion, diced
12 mini Yukon Gold potatoes, quartered
1 tsp dried thyme leaf (or 2 tsp fresh)
2 cups chicken stock, homemade or low-sodium storebought
1 cup milk (I use 2%)
2 Tbsp unbleached all-purpose flour
2 Tbsp chopped fresh flat-leaf parsley, plus extra for garnish
Directions
Preheat the broiler. Line a rimmed baking sheet with aluminum foil.
Season the fish on both sides with Old Bay Seasoning, and a sprinkle of kosher salt and black pepper. Broil for 10-12 minutes, depending on the thickness of the fish, turning the fish once. The fish should be almost cooked through; it will cook more in the soup.
In a Dutch oven or heavy soup pot, heat 1 tablespoon of the butter, plus the olive oil over low-medium heat. Stir in the onion, and sauté for a few minutes until the onion is translucent. Add the potatoes and thyme, and stir to coat with the butter and oil. Pour in the chicken stock.
Raise heat to high, to bring the liquid to a boil. Then, reduce to low, cover the pot, and cook for 15 minutes, stirring occasionally, until the potatoes are cooked through.
While the potatoes are cooking, in a small straight-sided sauce pan, heat the remaining 2 tablespoons of butter over medium heat. With a wooden spoon, stir in the flour, and continue stirring (you're making a roux) until the flour is completely incorporated and the roux coats the bottom of the pan. Pour in the milk, and stir until it thickens slightly. Then pour the whole bit into the pot with the potatoes.
Break the fish into large chunks, and add it to the soup. Taste, and season as needed with salt and plenty of black pepper; if you've used homemade stock, you might need as much as a teaspoon of salt. Finally, stir in the parsley.