Place the mushrooms in a small pot, and cover with 1 cup of the chicken stock. Bring to a simmer and cook to soften the mushrooms, 10 minutes. Remove the mushrooms with a slotted spoon and reserve both for later use.
Heat a large deep skillet or Dutch oven over medium-high heat, add the EVOO and the garlic, celery, bay leaves, carrots, fennel, onions, herb bundle and some salt and pepper. Cook partially covered 8 to 10 minutes. Stir in the tomato paste and cook 1 minute. Then add the wine, tomatoes and the remaining 2 cups chicken stock. Add the porcinis and their stock, minus the last few spoonfuls where grit may have settled. Simmer to thicken a bit and combine flavors then cool and store in the refrigerator for a make-ahead meal.
Heat a small skillet over medium heat with the pistachio nuts and toast until fragrant and golden. Finely chop or process in a food processor into coarse crumbs. Return the pan to heat and melt 4 tablespoons of the butter. Add the panko and toast until deep golden in color. Combine with the chopped nuts and season with salt and pepper or seafood seasoning. Store in an airtight container until ready to serve.
When ready to serve, remove the bay leaves and herb bundle. Reheat the stew, covered, over medium heat.
Pat the fish and sea scallops dry. Heat a drizzle of oil or thin layer of cooking spray over medium-high to high heat in each of the 2 skillets. Sprinkle the halibut with some seafood seasoning, salt and pepper. Sprinkle the scallops with a little salt. Cook the halibut seasoned-side down for 3 to 4 minutes. Flip and cook until opaque, 2 minutes more. Turn off the heat and reserve the fish in the pan. Cook the scallops scored-side down until the sugars develop and caramelize, then flip and cook 1 minute more. Remove to a plate and deglaze the pan with some vermouth. Swirl in the remaining 2 tablespoons butter and then add the parsley and lemon juice.
Cut the halibut into chunks. Ladle the stew into bowls and nestle in the halibut and scallops. Top with vermouth and lemon sauce and garnish with the pistachio breadcrumbs.