2 lb. mussels, scrubbed and debearded
2 lb. halibut, cut into 2-inch chunks
½ lemon, juiced (about 1 tbsp.)
2 tbsp. unsalted butter
¼ cup EVOO, plus more for drizzling
2 shallots, finely chopped
6 cloves garlic, thinly sliced or chopped
1 tbsp. fresh thyme, chopped, or 1 tsp. dried
1 tbsp. fresh oregano, chopped, or 1 tsp. dried
1 tbsp. Calabrian chile paste or 1½ tsp. crushed red pepper
½ cup dry (white) vermouth or white wine
1 can (14 oz.) fire-roasted crushed or diced tomatoes
1 cup (8 oz.) tomato sauce or 1 cup passata
Fresh basil leaves, torn
1 loaf ciabatta, halved
Handful fresh parsley, coarsely chopped
Flaky sea salt
Rinse the mussels in a colander and gently shake. Discard any open mussels. Pat halibut dry, then squeeze lemon juice over it and season with salt and pepper. Preheat broiler.
In a large, deep lidded skillet over medium-high heat, melt butter with EVOO. Once butter is melted, add halibut and cook until brown and crispy, 3 to 4 minutes. Turn and cook 1 minute more, then transfer to a plate. Add the shallots, garlic, thyme, oregano, and chile paste and season with salt, stirring for 2 minutes. Pour in vermouth or wine and simmer until reduced by half, 1 to 2 minutes. Stir in tomatoes, tomato sauce, and mussels. Cover and cook until mussels open, 5 to 7 minutes. Discard any mussels that didn't open. Stir in basil. Gently nestle halibut into pot and reduce heat to low. Cook until fish is warmed through, about 1 minute.
Lay bread on baking sheet and broil until evenly charred, 1 to 2 minutes, rotating sheet if needed. Drizzle EVOO over the bread and sprinkle with parsley and flaky sea salt. Slice into large chunks.
Take the pot and the bread to the table. Serve family-style along with a green salad.