Place chopped parsley, orange zest, olives, garlic, salt and red pepper flakes in a food processor and pulse a few times to combine. Scrape down the sides and add olive oil. Process until a uniformly chunky texture is achieved.

Allow gremolata to sit at room temperature while you prepare the cioppino, to allow flavors to fully bloom.

Prepare a stockpot with a steamer basket insert. Bring 2 cups of water to boil, reduce heat to a simmer and steam mussels and clams until they just open, about 5-8 minutes. Remove pot from heat and place opened mussels and clams in a bowl. Discard any that don’t open and reserve the steaming liquid, about 2 cups.

In a large dutch oven or stockpot, heat olive oil over medium until shimmering. Add chopped onion, fennel and a pinch of salt, and sauté until onion is softened, about 8-10 minutes. Add minced garlic, roasted red peppers, oregano and thyme. Sauté until garlic is fragrant and most liquid has evaporated.

When the mixture looks dry and sticky, add white wine. Scrape up any bits clinging to the bottom. Bring to a boil and simmer for 5 minutes.

Crush whole tomatoes by hand and add to the mixture along with any juices, seafood stock, and reserved steaming liquid. Simmer for 20 minutes uncovered. Taste and adjust salt.

Add whitefish and shrimp to the pot and simmer covered for 2-3 minutes, until fish is opaque and shrimp are curled and pink.

Remove pot from heat and stir in mussels and clams. Taste and adjust salt. Serve immediately topped with the gremolata.