Brodet Croatian Fish Stew

Name: Brodet (Croatian Fish Stew)
Ingredients: 1 cup packed parsley leaves; 1⁄2 cup olive oil, plus more; 1⁄4 cup fresh lemon juice; 14 cloves garlic, thinly sliced; Kosher salt and freshly ground black pepper, to taste; 1 lb. skinless monkfish fillets, pin bones removed; 1 lb. skinless sea bass fillets, pin bones removed; 10 oz. raw medium shrimp, peeled and deveined, tails removed; 6 raw, unpeeled langoustines (optional), heads on; 1 lb. Yukon gold potatoes, peeled and thinly sliced; 2 small leeks, white and light green parts only, halved and thinly sliced; 1 large red onion, thinly sliced; 1 large yellow onion, thinly sliced; 1 cup dry white wine; 1 (28-oz.) can whole peeled tomatoes, crushed by hand